74917 Community-Based Landslide Risk Reduction Community-Based Landslide Risk Reduction Managing Disasters in Small Steps Malcolm G. Anderson Elizabeth Holcombe Washington, DC © 2013 International Bank for Reconstruction and Development / The World Bank 1818 H Street NW, Washington DC 20433 Telephone: 202-473-1000; Internet: www.worldbank.org Some rights reserved 1 2 3 4 16 15 14 13 This work is a product of the staff of The World Bank with external contributions. Note that The World Bank does not necessarily own each component of the content included in the work. The World Bank therefore does not warrant that the use of the content contained in the work will not infringe on the rights of third parties. The risk of claims resulting from such infringement rests solely with you. The findings, interpretations, and conclusions expressed in this work do not necessarily reflect the views of The World Bank, its Board of Executive Directors, or the governments they represent. The World Bank does not guarantee the accuracy of the data included in this work. The boundaries, colors, denominations, and other information shown on any map in this work do not imply any judgment on the part of The World Bank concerning the legal status of any territory or the endorsement or acceptance of such boundaries. Nothing herein shall constitute or be considered to be a limitation upon or waiver of the privileges and immunities of The World Bank, all of which are specifically reserved. Rights and Permissions This work is available under the Creative Commons Attribution 3.0 Unported license (CC BY 3.0) http://creativecommons.org/ licenses/by/3.0. Under the Creative Commons Attribution license, you are free to copy, distribute, transmit, and adapt this work, including for commercial purposes, under the following conditions: Attribution—Please cite the work as follows: Anderson, Malcolm G., and Elizabeth Holcombe. 2013. Community-Based Landslide Risk Reduction: Managing Disasters in Small Steps. Washington, D.C.: World Bank. doi:10.1596/978-0-8213-9456-4. License: Creative Commons Attribution CC BY 3.0 Translations—If you create a translation of this work, please add the following disclaimer along with the attribution: This translation was not created by The World Bank and should not be considered an official World Bank translation. The World Bank shall not be liable for any content or error in this translation. All queries on rights and licenses should be addressed to the Office of the Publisher, The World Bank, 1818 H Street NW, Washington, DC 20433, USA; fax: 202-522-2625; e-mail: pubrights@worldbank.org. ISBN (paper): 978-0-8213-9456-4 ISBN (electronic): 978-0-8213-9491-5 DOI: 10.1596/978-0-8213-9456-4 Cover photo: © iStockphotocom/luoman; cover design: Drew Fasick Library of Congress Cataloging-in-Publication Data Anderson, M. G.
  Community-based landslide risk reduction : managing disasters in small steps / Malcolm G. Anderson, Elizabeth Holcombe.
       p. cm.
  Includes bibliographical references and index.
  ISBN 978-0-8213-9456-4 — ISBN 978-0-8213-9491-5 (electronic)
 1.  Landslide hazard analysis. 2.  Landslides—Risk assessment.  I. Holcombe, Elizabeth. II. Title. 
  QE599.2.A53 2013
 363.34'9—dc23 
                                                                             2012030220 Contents PREFACE xxi ACKNOWLEDGMENTS xxxiii ABOUT THE AUTHORS xxxv ABBREVIATIONS xxxvii 1 FOUNDATIONS: REDUCING LANDSLIDE RISK IN COMMUNITIES 1 1.1 Key chapter elements 1 1.1.1 Coverage 1 1.1.2 Documents 1 1.1.3 Steps and outputs 2 1.1.4 Community-based aspects 2 1.2 Getting started 2 1.2.1 Briefing note 2 1.2.2 What is unique about MoSSaiC? 5 1.2.3 Guiding principles 6 1.2.4 Risks and challenges 6 1.3 Disaster risk: context and concepts 7 1.3.1 Global disaster risk 7 1.3.2 Disaster risk management 11 1.3.3 Recent influences on disaster risk management policy and implications for MoSSaiC 14 1.3.4 Landslide risk and other development policy issues 23 1.4 MoSSaiC 25 1.4.1 Overview 25 1.4.2 MoSSaiC: The science basis 26 1.4.3 MoSSaiC: The community basis 29 1.4.4 MoSSaiC: The evidence base 34 1.4.5 MoSSaiC project components 34 1.4.6 MoSSaiC pilots 35 1.5 Starting a MoSSaiC intervention 42 1.5.1 Define the project scale 42 1.5.2 Define the project teams and stakeholders 42 v 1.5.3 Adhere to safeguard policies 45 1.5.4 Establish a project logframe 45 1.5.5 Brief key leaders 47 1.6 Resources 48 1.6.1 Who does what 48 1.6.2 Chapter checklist 48 1.6.3 References 48 2 PROJECT INCEPTION: TEAMS AND STEPS 55 2.1 Key chapter elements 55 2.1.1 Coverage 55 2.1.2 Documents 55 2.1.3 Steps and outputs 56 2.1.4 Community-based aspects 56 2.2 Getting started 56 2.2.1 Briefing note 56 2.2.2 Guiding principles 57 2.2.3 Risks and challenges 57 2.2.4 Adapting the chapter blueprint to existing capacity 58 2.3 Establishing the MoSSaiC Core Unit 60 2.3.1 Rationale 60 2.3.2 MCU roles and responsibilities 62 2.3.3 MCU membership 65 2.4 Identifying the government task teams 65 2.4.1 Mapping task team 67 2.4.2 Community liaison task team 67 2.4.3 Landslide assessment and engineering task team 68 2.4.4 Technical support task team 69 2.4.5 Communications task team 69 2.4.6 Advocacy task team 69 2.5 Identifying the community task teams 71 2.5.1 Community residents 71 2.5.2 Construction task team 73 2.5.3 Landowners 73 2.6 Integration of MoSSaiC teams and project steps 74 2.6.1 Team structure and reporting lines 74 2.6.2 Integrating teams with project steps 74 2.6.3 Establishing a user group community 75 2.7 Resources 78 2.7.1 Who does what 78 2.7.2 Chapter checklist 79 2.7.3 References 79 3 UNDERSTANDING LANDSLIDE HAZARD 81 3.1 Key chapter elements 81 3.1.1 Coverage 81 3.1.2 Documents 81 3.1.3 Steps and outputs 82 3.1.4 Community-based aspects 82 v i   CO N T E N T S 3.2 Getting started 82 3.2.1 Briefing note 82 3.2.2 Guiding principles 83 3.2.3 Risks and challenges 84 3.2.4 Adapting the chapter blueprint to existing capacity 85 3.3 Landslide types and those addressed by MoSSaiC 85 3.3.1 Types of slope movement and landslide material 85 3.3.2 Landslide geometry and features 87 3.3.3 Landslide triggering events: Rainfall and earthquakes 87 3.3.4 Slope stability over time 91 3.4 Slope stability processes and their assessment 93 3.4.1 Landslide preparatory factors and triggering mechanisms 93 3.4.2 Overview of slope stability assessment methods 93 3.4.3 GIS-based landslide susceptibility mapping 95 3.4.4 Direct landslide mapping 97 3.4.5 Empirical rainfall threshold modeling 98 3.4.6 Physically based slope stability modeling 99 3.5 Slope stability variables 101 3.5.1 Rainfall events 101 3.5.2 Slope angle 103 3.5.3 Material type and properties 104 3.5.4 Slope hydrology and drainage 107 3.5.5 Vegetation 108 3.5.6 Loading 111 3.6 Scientific methods for assessing landslide hazard 112 3.6.1 Coupled dynamic hydrology and slope stability models 113 3.6.2 Resistance envelope method for determining suction control 116 3.6.3 Modeling the impact of small retaining walls 117 3.7 Resources 119 3.7.1 Who does what 119 3.7.2 Chapter checklist 120 3.7.3 Rainfall thresholds for triggering landslides 120 3.7.4 CHASM principle equation set 120 3.7.5 Static hydrology retaining wall stability analysis 122 3.7.6 References 123 4 SELECTING COMMUNITIES 129 4.1 Key chapter elements 129 4.1.1 Coverage 129 4.1.2 Documents 129 4.1.3 Steps and outputs 130 4.1.4 Community-based aspects 130 4.2 Getting started 130 4.2.1 Briefing note 130 4.2.2 Guiding principles 131 4.2.3 Risks and challenges 131 4.2.4 Adapting the chapter blueprint to existing capacity 132 4.3 Defining the community selection process 132 4.3.1 Approaches to comparing levels of landslide risk at multiple locations 134 4.3.2 Methods for community selection 136 4.3.3 Roles and responsibilities in community selection 140 CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   v i i 4.4 Landslide susceptibility and hazard assessment methods 140 4.4.1 Qualitative landslide hazard assessment: Field reconnaissance and hazard ranking methods 141 4.4.2 Qualitative landslide susceptibility mapping: GIS index overlay methods 146 4.4.3 Semi-quantitative and quantitative landslide susceptibility and hazard mapping methods 149 4.5 Assessing community vulnerability to landslides 151 4.5.1 Field reconnaissance and vulnerability ranking methods 153 4.5.2 GIS-based mapping methods for vulnerability assessment 155 4.6 Assessing landslide risk and confirming community selection 156 4.6.1 Combining the hazard and vulnerability information 157 4.6.2 Confirming selected communities 157 4.7 Preparing a base map for detailed community mapping 159 4.7.1 Useful features 159 4.7.2 Supporting data 159 4.7.3 Sources of spatial data 159 4.8 Resources 161 4.8.1 Who does what 161 4.8.2 Chapter checklist 162 4.8.3 References 162 5 COMMUNITY-BASED MAPPING FOR LANDSLIDE HAZARD ASSESSMENT 165 5.1 Key chapter elements 165 5.1.1 Coverage 165 5.1.2 Documents 165 5.1.3 Steps and outputs 166 5.1.4 Community-based aspects 166 5.2 Getting started 167 5.2.1 Briefing note 167 5.2.2 Guiding principles 168 5.2.3 Risks and challenges 169 5.2.4 Adapting the chapter blueprint to existing capacity 170 5.3 Deciding on how to work within a community 170 5.3.1 Community participation: Principles 170 5.3.2 Community participation: Practices 174 5.3.3 Community knowledge and participation in the mapping process 176 5.4 Community slope feature mapping 178 5.4.1 Hillside scale: Mapping overall topography and drainage 178 5.4.2 Household scale: Mapping the detail 182 5.4.3 Indicators of slope stability issues 185 5.4.4 Finalizing the community slope feature map 187 5.5 Qualitative landslide hazard assessment 188 5.5.1 Landslide hazard assessment for MoSSaiC projects 188 5.5.2 Identify landslide hazard zones 189 5.5.3 Identify the dominant landslide mechanisms 191 5.6 Physically based landslide hazard assessment 191 5.6.1 Models 191 5.6.2 Data for slope stability models 194 v i i i   CO N T E N T S 5.6.3 Using slope stability models 194 5.6.4 Analyzing the role of pore water pressure 198 5.6.5 Uncertainty in physically based landslide hazard assessment 199 5.6.6 Interpreting physically based landslide hazard assessment results 201 5.7 Prioritize zones for drainage interventions 203 5.7.1 Assign a potential drainage intervention to each zone 203 5.7.2 Draw an initial drainage plan 205 5.7.3 Assign priorities to the different zones 206 5.7.4 Sign-off on the map and the proposed intervention 207 5.8 Resources 208 5.8.1 Who does what 208 5.8.2 Chapter checklist 209 5.8.3 References 209 6 DESIGN AND GOOD PRACTICE FOR SLOPE DRAINAGE 213 6.1 Key chapter elements 213 6.1.1 Coverage 213 6.1.2 Documents 213 6.1.3 Steps and outputs 214 6.1.4 Community-based aspects 214 6.2 Getting started 214 6.2.1 Briefing note 214 6.2.2 Guiding principles 215 6.2.3 Risks and challenges 215 6.2.4 Adapting the chapter blueprint to existing capacity 216 6.3 Principles and tools for general alignment of drains 217 6.3.1 Drainage alignment patterns and principles 218 6.3.2 Calculating drain flow and drain dimensions 222 6.3.3 Estimating surface water discharge 223 6.3.4 Estimating the discharge from houses 226 6.3.5 Estimating dimensions for main drains 227 6.3.6 Example to demonstrate intercept drain effectiveness 227 6.3.7 Example to demonstrate the impact of drain channel slope on flow capacity 228 6.3.8 Example to demonstrate the impact of household water 229 6.4 Drain types and detailed alignments 229 6.4.1 Intercept drains 231 6.4.2 Downslope drains 232 6.4.3 Footpath drains 232 6.4.4 Incomplete existing drainage 233 6.4.5 Drains above landslides to stabilize the slope 234 6.4.6 Incorporating debris traps into drain alignment 235 6.4.7 Proposed drainage plan 236 6.5 Drain construction specifications: materials and details 236 6.5.1 Reinforced concrete block drains 238 6.5.2 Low-cost, appropriate technology for drain construction 239 6.5.3 Combining different drain construction approaches 241 6.5.4 Construction design details 242 6.6 Incorporating household water capture into the plan 242 6.6.1 Houses requiring roof guttering 242 6.6.2 Rainwater harvesting 244 CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   i x 6.6.3 Gray water capture 246 6.6.4 Connection to the drainage network 247 6.6.5 Hurricane strapping 249 6.7 Signing off on the final drainage plan 250 6.7.1 Drawing the final drainage plan and estimating costs 250 6.7.2 Community agreement 251 6.7.3 Formal approval and next steps 253 6.8 Resources 254 6.8.1 Who does what 254 6.8.2 Chapter checklist 255 6.8.3 Local designs for concrete drains, catchpits, and baffles 255 6.8.4 References 259 7 IMPLEMENTING THE PLANNED WORKS 261 7.1 Key chapter elements 261 7.1.1 Coverage 261 7.1.2 Documents 261 7.1.3 Steps and outputs 262 7.1.4 Community-based aspects 262 7.2 Getting started 262 7.2.1 Briefing note 262 7.2.2 Guiding principles 265 7.2.3 Risks and challenges 265 7.2.4 Adapting the chapter blueprint to existing capacity 266 7.3 Preparing work packages 266 7.3.1 Prepare a bill of quantities 268 7.3.2 Define work packages 271 7.3.3 Prepare a plan for procurement of materials 272 7.3.4 Prepare detailed construction specifications 272 7.3.5 Compile documents for each work package 272 7.4 The tendering process 274 7.4.1 Identifying contractors from the community 274 7.4.2 Briefing potential contractors 274 7.4.3 Evaluating tenders and awarding contracts 276 7.4.4 Contractors and safeguard policies 277 7.5 Implementing the works: on-site requirements 278 7.5.1 Importance of site supervision 278 7.5.2 Beginning construction: Excavation and alignment requirements 279 7.5.3 Ensure that water can enter drains 281 7.5.4 Capture household roof water 282 7.5.5 Connect household water to drains 284 7.6 Implementing the works: good practices 285 7.6.1 Cast concrete in good weather 285 7.6.2 Store materials securely 287 7.6.3 Keep an inventory 287 7.6.4 Provide access for residents 287 7.6.5 Minimize leakage from pipes 288 7.7 Implementing the works: practices to be avoided 288 7.7.1 Wasted materials and no surface water capture 288 7.7.2 Restricted capacity of footpath drains 288 x   CO N T E N T S 7.7.3 Hazardous access for residents 291 7.7.4 Construction detailing notes 291 7.8 Signing off on the completed works 291 7.9 Postconstruction bioengineering 292 7.9.1 What is bioengineering? 293 7.9.2 The effect vegetation on slope stability 293 7.9.3 Vegetation and urban slope management 294 7.10 Resources 297 7.10.1 Who does what 297 7.10.2 Chapter checklist 298 7.10.3 Low-cost appropriate construction methods 298 7.10.4 Questionable or corrupt practices in construction 300 7.10.5 References 301 8 ENCOURAGING BEHAVIORAL CHANGE 305 8.1 Key chapter elements 305 8.1.1 Coverage 305 8.1.2 Documents 305 8.1.3 Steps and outputs 306 8.1.4 Community-based aspects 306 8.2 Getting started 306 8.2.1 Briefing note 306 8.2.2 Guiding principles 307 8.2.3 Risks and challenges 308 8.2.4 Adapting the chapter blueprint to existing capacity 309 8.3 Adoption of change: from risk perception to behavioral change 309 8.3.1 The behavioral change process 309 8.3.2 Understanding stakeholder perceptions 312 8.3.3 Combining knowledge and action 314 8.4 Communication purpose and audience 315 8.4.1 Defining communication purposes and functions 317 8.4.2 Identifying audiences 317 8.5 Forms of communication and project messages 317 8.5.1 Direct communication, consultation, and dialogue 320 8.5.2 Community demonstration sites and show homes 321 8.5.3 Written and visual materials for communities 323 8.5.4 TV, radio, and newspaper coverage 324 8.5.5 Scientific and professional publications 328 8.5.6 Finalizing project messages 329 8.6 Ways of building local capacity 329 8.6.1 For individuals 330 8.6.2 For teams 331 8.6.3 For politicians 331 8.6.4 For communities 332 8.6.5 For all user groups 333 8.7 Finalizing the integrated behavioral change strategy 334 8.7.1 Encouraging adoption of good drain maintenance practices 334 8.7.2 The integrated behavior change strategy 338 CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   x i 8.8 Resources 340 8.8.1 Who does what 340 8.8.2 Chapter checklist 341 8.8.3 MoSSaiC certification 341 8.8.4 References 342 9 PROJECT EVALUATION 345 9.1 Key chapter elements 345 9.1.1 Coverage 345 9.1.2 Documents 345 9.1.3 Steps and outputs 346 9.1.4 Community-based aspects 346 9.2 Getting started 346 9.2.1 Briefing note 346 9.2.2 Guiding principles 349 9.2.3 Risks and challenges 349 9.2.4 Adapting the chapter blueprint to existing capacity 350 9.3 Data requirements for project evaluation 350 9.3.1 MoSSaiC project evaluation data 350 9.3.2 Community knowledge and project evaluation data 352 9.4 Project outputs: evaluating immediate impact 353 9.4.1 Typical key performance indicators 353 9.4.2 Output key performance indicators for MoSSaiC projects 354 9.5 Project outcomes: evaluating medium-term performance 354 9.5.1 Observed slope stability 355 9.5.2 Rainfall and slope stability information 357 9.5.3 Cracks in houses 358 9.5.4 Surface and subsurface water 360 9.5.5 Drain performance 362 9.5.6 Environmental health benefits 362 9.5.7 Economic appraisal: Project value for money 364 9.5.8 Adoption of good landslide risk reduction practices 367 9.5.9 Development of new landslide risk reduction policies 367 9.5.10 Finalizing the project evaluation process 369 9.6 Addressing landslide risk drivers over the longer term 370 9.6.1 Disaster risk reduction and climate proofing 370 9.6.2 Connecting hazard reduction and insurance 371 9.6.3 Anticipating future disaster risk scenarios 374 9.7 Resources 379 9.7.1 Who does what 379 9.7.2 Chapter checklist 379 9.7.3 Installing crack monitors 379 9.7.4 Installing and using simple piezometers 380 9.7.5 Cost-benefit analysis 381 9.7.6 References 383 GLOSSARY 387 INDEX 393 x i i   CO N T E N T S FIGURES 1.1 Global landslide risk 3 1.2 MoSSaiC premises, vision, and foundations 4 1.3 Number of great natural catastrophes and associated economic losses worldwide, 1950–2010 8 1.4 Normalized losses from U.S. Gulf and Atlantic hurricane damage, 1900–2005 9 1.5 Exposure and fatalities associated with rainfall-triggered landslides, by income class 10 1.6 Global rainfall-triggered landslide fatalities 11 1.7 Disaster risk management options 14 1.8 Societal landslide risk in Hong Kong SAR, China 15 1.9 International advocacy landscape for disaster risk reduction 15 1.10 UN disaster response organizational framework 16 1.11 Benefit-cost ratio for hurricane-proofing prevention measures for houses in Canaries and Patience, St. Lucia 18 1.12 Mitigation benefit-cost ratio for wood frame building in Canaries, St. Lucia, with and without the effect of climate change 19 1.13 Efficiency of risk management instruments and occurrence probability 19 1.14 Evolution of social fund objectives and activities 22 1.15 Population growth and urbanization drivers of landslide risk 24 1.16 MoSSaiC architecture—integrating science, communities, and evidence 27 1.17 Housing stock can reflect community vulnerability 28 1.18 Stakeholder connections in Guatemala City’s precarious settlements, showing how money flows around, but not into, the settlements 30 1.19 Learning from community residents 32 1.20 Effects of prompt and informed action 32 1.21 MoSSaiC components 36 1.22 Typical communities and risk drivers for MoSSaiC interventions 40 1.23 Countries with damages from disasters exceeding 1 percent of GDP 41 1.24 Impact of Hurricane Allen (1980) on the economy of St. Lucia 41 1.25 MoSSaiC is applicable to many locations outside the Eastern Caribbean 41 2.1 Five missions of the MoSSaiC core unit 63 2.2 Mapping team from a national disaster management agency demonstrates GIS software to MCU team leader 67 2.3 Coordinating with Social Development Ministry and community residents on site 68 2.4 Examples of landslide assessment and engineering task team responsibilities 68 2.5 Technical team training course attendees: Sharing and developing expertise across ministries 69 2.6 Aspects of communication 70 2.7 On-site briefing 70 2.8 Media film elected officials during a MoSSaiC project 71 2.9 Funding agency staff on site at initial stage of MoSSaiC project 71 2.10 Aspects of community resident involvement in MoSSaiC 72 2.11 Briefing potential contractors on site after calling for expressions of interest from within the community 73 2.12 Contractor briefs government technical officers on project implemented in his community 74 2.13 Typical MoSSaiC team reporting structure 75 2.14 User group forum activities 75 3.1 Characteristics of rotational and translational slides in predominantly weathered materials 87 3.2 Definitional features of a landslide 88 3.3 Typical surface and subsurface water sources and flow paths associated with unauthorized construction on hillslopes 89 3.4 Rotational and translational landslides 90 3.5 Distribution of seismicity during the 2001 El Salvador earthquakes 91 3.6 Aerial view of earthquake-triggered landslide in Las Colinas, El Salvador, January 13, 2001 91 CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   x i i i 3.7 Progressive landslide 92 3.8 Postfailure slope stability 93 3.9 Classified spatial factor data 97 3.10 Landslide susceptibility map 98 3.11 Three landslide inventory maps 98 3.12 Global rainfall intensity-duration thresholds 99 3.13 Discretization of a slope into slices to facilitate slope stability calculations 100 3.14 Preparatory factors that can influence slope stability 102 3.15 Hurricane Tomas over the Eastern Caribbean, 2010 103 3.16 An Abney level and its use 104 3.17 Slope benched by resident to build a house 104 3.18 Typical weathering profiles of tropical soils 105 3.19 Weathering profiles 106 3.20 Shear box used to determine soil strength parameters 106 3.21 Exposed soil pipe some 30 cm below the soil surface 106 3.22 Definition of the planimetric contributing area at two locations in a hypothetical landscape 107 3.23 Shallow rotational slip on an 18-degree slope at the foot of an extensive hillside 108 3.24 Common drainage issues in unauthorized communities 109 3.25 Examples of adverse and beneficial effects of vegetation on slopes 110 3.26 Model of post-landslide vegetation succession for the Caribbean 111 3.27 Examples of incremental construction 112 3.28 Examples of reconstruction on former landslide sites 113 3.29 Representation of a slope cross-section for analysis in CHASM software 114 3.30 CHASM representation of a natural hillslope 115 3.31 Outputs from a CHASM simulation 116 3.32 Superimposition of resistance and strength envelopes 117 3.33 Resistance envelope plots 117 3.34 Inadequate retaining wall design 118 3.35 A simple retaining wall geometry used for the retaining wall analysis 122 4.1 Top-down and bottom-up community selection methods 137 4.2 Field reconnaissance 143 4.3 Method for developing a national landslide risk index map for Cuba 149 4.4 Quantitative GIS-based hazard map for Tegucigalpa, Honduras 150 4.5 Resilience of structures depending on construction type 153 4.6 Generating the base map from a topography map and an aerial photo 160 5.1 Access and control over resources in Ethiopia by women and men 173 5.2 Listening to community residents is important 175 5.3 Engaging community representatives and guides in identifying slope features and landslide issues 176 5.4 Discussing slope stability and drainage hazards around residents’ houses 177 5.5 Informal group discussion held at an accessible location 177 5.6 Local community hall used as venue for hearing residents’ views 178 5.7 Community base map and supplementary aerial photograph 179 5.8 Topographic elements to be distinguished and identified in the field 180 5.9 Example of a tropical hillslope profile illustrating common weathering features 180 5.10 Soil depth and stability 180 5.11 Seepage occurring in dry weather conditions where there is no sign of a zone of topographic convergence 181 5.12 Looking for natural and altered slope drainage 182 5.13 Potential landslide hazard driver: Cutting platforms to build houses 183 5.14 Potential landslide hazard driver: Household roof and gray water discharged directly onto slopes 184 5.15 Potential landslide hazard driver: Failure of poorly designed and constructed water storage structure 185 5.16 Evidence of minor slope movement 186 5.17 Cracks in a wall: Past slope instability or poor construction? 186 x i v   CO N T E N T S 5.18 Example of a community slope feature map showing household-level detail 187 5.19 Piped water supplied to unauthorized communities 189 5.20 The qualitative landslide hazard assessment process 190 5.21 Example of a slope process zone map with supporting observations and interpretations 192 5.22 Typical slope selected for stability analysis 195 5.23 Zone E of the example community with two slope cross-sections marked for analysis 196 5.24 Model configuration and predicted location of landslides 197 5.25 Predicted landslide locations and estimated runout 198 5.26 Predicted improvements in the factor of safety for different drainage interventions 198 5.27 Example of heterogeneity in angle of internal friction and cohesion, classified by weathering grade 200 5.28 Number of geotechnical engineers selecting various friction angles as characteristic for a given set of soil strength data 200 5.29 Effect of soil parameter variability on CHASM simulation results 201 5.30 Slope stability modeling workshop for landslide assessment and engineering task team 202 5.31 Complete community-based landslide hazard assessment process for MoSSaiC interventions 204 5.32 Example of an initial drainage plan 205 5.33 Proposed midslope intercept drain alignment 206 6.1 Iterative design process for developing final drainage plan 219 6.2 Idealized hillside drainage plan showing intercept and downslope drains 220 6.3 Generalized alignment for use with top-of-slope intercept drains 220 6.4 Intercept drain built on a slope with few restrictions to alignment 220 6.5 Drain alignment complexities 221 6.6 Network of small intercept drains intercepting surface water along entire uppermost contour of slope 221 6.7 Downslope drain 221 6.8 Drain alignment to minimize surface and immediate subsurface water flow into previously failed material 222 6.9 Drain aligned to intercept surface water and routed around a major preexisting landslide 222 6.10 Drain alignment for site of progressive failure 222 6.11 Iterative process for designing drain alignments and dimensions 223 6.12 Estimating observed drain flows 228 6.13 Impact of drain gradient on flow velocity and discharge 229 6.14 Effect of household water drainage in a typical community 230 6.15 Potential effectiveness of household drainage measures 230 6.16 Drain alignment must be correctly specified in communities 231 6.17 Main cross-slope intercept drain constructed on a 35 degree slope angle 231 6.18 Poor practice: Downslope drain construction begun at top of hillside rather than base of slope 232 6.19 Examples of footpath and footpath drains being constructed simultaneously 233 6.20 Incomplete and damaged drains 234 6.21 Drain construction above a failed slope 235 6.22 Postconstruction maintenance: Keeping drains free of debris 235 6.23 Debris trap in an urban area of Hong Kong, SAR, China 235 6.24 Example of an initial drainage plan 237 6.25 Example of a draft final drainage plan 237 6.26 Rubble wall as part of drain construction 239 6.27 Example of concrete block drain design 239 6.28 Shipping construction material to site can be expensive 240 6.29 Installation of plastic-lined drain 240 6.30 Community innovation and skills at work after project completion 241 6.31 Combination of block drain and low-cost drain 241 CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   x v 6.32 Number of days slope surface is saturated per year with and without household water capture 242 6.33 Process for incorporating household water capture into the drainage plan 244 6.34 Retrofitting roof guttering 244 6.35 Rainwater harvesting 245 6.36 A system for filtering and purifying water for human consumption 245 6.37 Cost components of small domestic rainwater harvesting system 246 6.38 Capturing gray water from showers and washing machines 246 6.39 Gray water and roof water connections to block drain 247 6.40 Household connections to main drains 248 6.41 Concrete chambers connecting water from multiple houses to a single collection point with an outflow pipe to a main drain 249 6.42 Fragile roof structure 249 6.43 Hurricane strapping ties 250 6.44 Roof hurricane strap 250 6.45 Extracts from a final drainage plan for agreement with stakeholders and sign-off 252 6.46 Community involvement in finalizing the drainage plan 253 6.47 U-channel 256 6.48 Baffle wall junction 256 6.49 Typical debris/sand trap 257 6.50 Stepped channel 258 6.51 Catchpit junction 259 7.1 MCU meeting to agree on responsibilities during construction process 263 7.2 Contractor site meeting 264 7.3 Modifications to roof structure for roof guttering installation 269 7.4 Downpipe installation detail 269 7.5 Roof guttering and downpipe components 270 7.6 Connection of downpipe to drain awaits purchase of a connecting section 270 7.7 Spreadsheet to assist in developing bills of quantities 270 7.8 Confirming with residents connection of households to drains 271 7.9 On-site meetings with potential community contractors 274 7.10 Some issues to address during on-site briefing 275 7.11 Double handling of materials can require temporary storage 276 7.12 Contractor signing on site with implementing agency representative 277 7.13 Importance of training in reducing rework costs 278 7.14 Clear markings help remove issues of ambiguity for site supervisor 279 7.15 Site supervisor is critical to project success and to ensuring good construction practice 279 7.16 Supervision issue: Large numbers of residents engaging with contractors 280 7.17 Example of detailed alignment issue encountered at construction start 280 7.18 Self-cleaning stepped drains 281 7.19 Finished drain wall height same as adjoining ground surface 282 7.20 Weep hole formation 282 7.21 Drain construction providing for eventual connection with gray water pipes 282 7.22 Issues involved in roof repair 283 7.23 Newly installed roof guttering 283 7.24 Household roof water connections to main drains 284 7.25 Concrete connection chambers 285 7.26 Connecting water tank overflow pipes to nearby drains 286 7.27 Examples of drain bases 286 7.28 Providing adequate temporary access to houses during construction 287 7.29 Using sleeving to join drainage pipe sections 288 7.30 Illustrations of frequently overlooked drainage design and construction details 290 7.31 Drain built with inappropriately high sidewalls 290 7.32 Identify maximum drain capacity adjacent to footpath steps 291 7.33 Some construction practices can pose dangers to small children 291 x v i   CO N T E N T S 7.34 Typical development of plant communities under a bioengineering and maintenance program 293 7.35 Lateral root spread 294 7.36 Four vegetation covers typically found on hillsides housing vulnerable communities 296 7.37 Bioengineered slope in Hong Kong SAR, China 296 7.38 Choosing a debris trap location 298 7.39 Welding in-situ and completion of debris trap 299 7.40 Construction of low-cost drain 300 8.1 The Johari Window for increasing common ground and knowledge among stakeholders 313 8.2 Show homes 322 8.3 Meeting invitation and project flier given to community residents at project start 325 8.4 Example of a leaflet or small poster to use in informal conversations with residents 325 8.5 Using posters to convey project messages 326 8.6 Media filming during construction 327 8.7 Opening frame of a MoSSaiC TV documentary 327 8.8 Community surveyor and contractor receive MoSSaiC certification 331 8.9 MoSSaiC training in the Eastern Caribbean 331 8.10 Building team capacity 332 8.11 Combined slope process zone map and initial drainage plan 332 8.12 Building political capacity 332 8.13 Building community capacity 333 8.14 Building regional capacity: In conferences and on site 334 8.15 Unintended consequences of drainage interventions 335 8.16 Absence of building controls can lead to inappropriate construction 336 8.17 Importance of promoting community clean-up days 337 8.18 Debris traps should be installed and cleared regularly 337 8.19 Debris collection and disposal 338 9.1 Links between project objectives and overall project success 347 9.2 Residents showing issues to be addressed by MoSSaiC interventions 353 9.3 Maximum observed flow level in a MoSSaiC drain during Hurricane Tomas 353 9.4 Landslide in an area immediately adjacent to a slope successfully stabilized by a MoSSaiC intervention 356 9.5 Daily and cumulative rainfall with associated return periods for a location in St. Lucia, October 2008 358 9.6 Benchmarking major rainstorms with satellite imagery 360 9.7 Assessing and monitoring structural cracks 361 9.8 Surface and subsurface water undermining stability of house structures 361 9.9 Convergence of water upslope results in slope instability and property destruction on shallow slope 362 9.10 Drain performance 362 9.11 Stagnant water and disease transmission: The health consequences of poor drainage 363 9.12 Laboratory-confirmed dengue hemorraghic fever in the Americas prior to 1981 and 1981–2003 364 9.13 MoSSaiC and mosquito breeding habitats 364 9.14 Dynamics of policy making 368 9.15 Process of strategic incrementalism 369 9.16 Generalized impact of MoSSaiC interventions on reducing the burden of coping 372 9.17 Model used in St. Lucia for hurricane-resistant home improvement program for low-income earners 375 9.18 Hypothetical calculation base for the resource gap 376 9.19 Media recognition of the world’s urban population crossing the 50 percent mark 377 9.20 Conceptual diagram of a scenario funnel 377 9.21 Crack monitoring gauge and crack record charts 380 9.22 Installing piezometers 381 9.23 Components of an integrated model of landslide hazard and risk assessment 382 CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   x v i i TABLES P.1 Critical questions and decisions addressed in this book xxxi 1.1 The key teams and tasks in MoSSaiC 5 1.2 Categories of catastrophe 9 1.3 Disaster risk management components 13 1.4 Lessons learned from World Bank natural disaster projects 17 1.5 Percentage of owner occupancy, unauthorized housing, and squatter housing by country income group, 1990 25 1.6 The foundations of MoSSaiC 26 1.7 Coping mechanisms deployed by individual residents in vulnerable communities to reduce landslide risk 31 1.8 Value of community engagement 33 1.9 Basic MoSSaiC outputs and outcomes providing evidence for ex ante landslide mitigation 35 1.10 Broad impacts of community-based landslide risk reduction program in St. Lucia and Dominica, 2005–10 35 1.11 MoSSaiC framework 36 1.12 Characteristics of MoSSaiC project locations in the Eastern Caribbean, 2004–10 40 1.13 Magnitudes of scale-up 42 1.14 Issues to consider when scaling up MoSSaiC 43 1.15 Likely stakeholders and their potential involvement in a MoSSaiC intervention 44 1.16 Typical safeguard policy considerations 46 1.17 Example of a logframe format 47 2.1 Key characteristics of highly successful social development projects 57 2.2 Typical landslide risk management project cycle 60 2.3 The active Samaritan’s Dilemma 61 2.4 Landslide risk reduction issues that need to be offset by a policy entrepreneur 62 2.5 Government task team selection factors 66 2.6 Task teams and guidance notes 66 2.7 Summary template of MoSSaiC project teams, steps, and milestones 76 3.1 Typical landslide risk management project steps and associated scientific basis for MoSSaiC 84 3.2 Slope instability classification 87 3.3 Arias intensity and associated landslide categories 91 3.4 Landslide velocity scale 92 3.5 Factors determining slope stability and associated assessment methods 94 3.6 Spatial scales of landslide triggering mechanisms, preparatory factors and anthropogenic influences 94 3.7 Advantages and disadvantages of different forms of landslide susceptibility and hazard assessment 96 3.8 Vegetation influences on slope stability 110 3.9 Units for the parameters used in CHASM 121 3.10 Results of an illustrative standard static hydrology retaining wall stability analysis 123 4.1 Schematic representation of the basic data sets for landslide susceptibility, hazard, and risk assessment 135 4.2 Framework of potential data and analysis methods 138 4.3 Overview of environmental factors and their relevance to landslide susceptibility and hazard assessment 142 4.4 Typical sections of a slope reconnaissance form 144 4.5 Example of a landslide likelihood rating system 145 4.6 Main elements at risk used in landslide risk assessment studies and their spatial representation at four mapping scales 152 4.7 Typical sections of a slope reconnaissance form that relate to vulnerability assessment 154 4.8 Example of a numerical scoring system for landslide damage to houses 155 4.9 Typical components of a locally derived poverty index 156 4.10 Example of a risk rating matrix 157 4.11 Sample justification for community selection 158 x v i i i   CO N T E N T S 5.1 Types of community participation 172 5.2 Checklist for gender-sensitive risk assessment 174 5.3 Hillside scale features to mark on slope feature map 183 5.4 Household-scale contributors to slope instability to mark on slope feature map 185 5.5 Slope instability evidence to mark on slope feature map 187 5.6 Interpreting the influence of surface water infiltration on slope stability for different slope process zones 193 5.7 Quantitative physically based landslide hazard assessment models appropriate for use as part of MoSSaiC 194 5.8 Typical input parameters and their measurement for slope stability analysis 195 5.9 Summary of the physically based landslide hazard assessment process 202 5.10 Illustrative slope process zones and associated potential drainage measures 206 5.11 Illustrative prioritization of different drainage interventions in each of the zones 207 6.1 Calculations for estimating discharge into drains and drain size 224 6.2 Values of runoff coefficient C for the rational method 225 6.3 Drainage alignment summary for use in developing final drainage plan 238 6.4 Construction design details related to aspects of drain alignment 243 6.5 Initial costs for drain construction and for household water connections 251 6.6 Illustrative drawings for drain design 255 7.1 Yardsticks for selected community-based performance measures 265 7.2 Items to include when surveying houses identified for household water capture 269 7.3 Requirements and specifications to be developed for work packages 273 7.4 Illustrative safeguard checklist for contractors 277 7.5 Examples of frequently overlooked drainage design and construction details 289 7.6 Example of an informal schedule of construction defects and outstanding works 292 7.7 Decision aid for choosing a bioengineering technique 295 8.1 Steps in the ladder of adoption and associated MoSSaiC context 311 8.2 Behavior change factors: From motivation to action 312 8.3 Knowledge and action as part of the adoption of the MoSSaiC process 316 8.4 Questions to guide the design of a MoSSaiC communication strategy 316 8.5 Examples of local factors affecting communication 318 8.6 Examples of communication tools by mode, channel, and purpose 318 8.7 Deciding which forms of communication to use for each stakeholder audience 319 8.8 Examples of direct two-way communication tools for use throughout the MoSSaiC project process 320 8.9 Example uses of demonstration sites and show homes during the MoSSaiC project process 322 8.10 Examples of written/visual materials to be used during the MoSSaiC project process 324 8.11 Examples of media coverage during the MoSSaiC project process 327 8.12 Factors for the MCU to consider when commissioning a TV documentary 328 8.13 MoSSaiC capacity requirements at individual, organizational, and institutional levels 330 8.14 Examples of capacity-building tools by learning mode 330 8.15 Mapping the integrated behavioral change strategy 339 9.1 Data needed to evaluate outputs and outcomes by category of evaluation 352 9.2 Typical donor-focused key performance indicators for project outputs 354 9.3 Detailed MoSSaiC key performance indicators for project outputs 355 9.4 MoSSaiC key performance indicators for project outcomes 356 9.5 Landslides reported pre- and post-project with respect to major rainfall events in the Eastern Caribbean 359 9.6 Transmission routes of water-related diseases 363 9.7 Simple questions to help measure MoSSaiC project value for money 365 9.8 Requirements for achieving evidence-based policy in ex ante disaster risk reduction 369 9.9 Summary of MoSSaiC elements contributing to climate proofing 371 9.10 Holistic context of prevention, insurance, and coping strategies of individuals, communities, and governments 372 9.11 Design issues and challenges for linking risk reduction and insurance 373 9.12 Sources of postdisaster financing 376 CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   x i x Preface ABOUT MOSSAIC To achieve the vision and demonstrate the validity of these premises, three foundations MoSSaiC (Management of Slope Stability in need to be established: the scientific base, the Communities) is an integrated method for community base, and the evidence base for engaging policy makers, project managers, landslide risk reduction in this setting. practitioners, and vulnerable communities in 1. From a scientific standpoint, the root reducing urban landslide risk in developing causes of many landslides in urban com- countries. munities are aggravated by human activi- MoSSaiC was begun with the idea of com- ties that can addressed in relatively simple bining research, policy, and humanitarian and practical ways. A commonly observed interests to address rainfall-triggered land- situation is the negative effect of poor slide hazards through community-based drainage on the stability of slopes com- implementation of surface water manage- prised of weathered materials. This situa- ment measures in vulnerable urban commu- tion can often be remedied through the nities. The vision was to lay sustainable foun- construction of a strategically aligned net- dations for community-based landslide risk work of surface drains. Intercepting and reduction. conveying surface water runoff, household This vision was driven by the following gray water, and roof runoff to ravines and premises: main drains can significantly improve the • Disaster risk mitigation pays, and invest- stability of such slopes. ment in reducing rainfall-triggered land- 2. Community residents have detailed slide hazards in vulnerable communities knowledge of the slopes in their immediate can often be justified. vicinity—where there have been minor landslides, where surface water runs, how • Engaging existing government expertise the topography and vegetation have been for implementing risk reduction measures changed. This information on slope fea- can build capacity, embed good practice, tures is frequently the scale at which land- and change policy. slide-triggering processes operate and the • Ensuring community engagement from scale at which solutions can be found. Vul- start to finish can establish ownership of nerable communities are also where there solutions. is the greatest need for short-term employ- xxi ment (in constructing landslide mitigation ties. It provides guidance on how to imple- measures) and for embedding good slope ment MoSSaiC, evidence of what has worked management practices. Generally, govern- (and of potential risks and challenges), and ments have sufficient technical and mana- guidance on options that should be considered gerial skills that can be harnessed to design to make it work within a specific country. It and deliver appropriate landslide risk may be necessary to adapt the methodology reduction measures in communities. By for environments outside the Eastern Carib- creating a cross-disciplinary management bean—in terms of both general approach and unit from such a skill base, it is possible to specific implementation—to take into account embed MoSSaiC in government practice local landslide risk conditions and institu- and policy. tional contexts. 3. An evidence base for the effectiveness of This is not intended to be a book detailing such targeted landslide risk reduction construction methods. Specific solutions are measures was needed. MoSSaiC was not offered; rather the book presents a sum- started small, with a pilot intervention in mary of our experience, observations, and one community, a catalytic advocate in research. In that regard, two broad issues government, and a small team of in-house deserve emphasis: ensuring the long-term fea- project managers and practitioners. On the sibility of the approach, and being sensitive to evidence of its success, further govern- the scale and extent of the landslide risk prob- ment funding and demand for more inter- lem. ventions followed. This evidence was in • To ensure long-term sustainability of the form of finished construction works, MoSSaiC projects requires the identifica- improved stability of slopes, community tion of localized landslide-triggering pro- endorsement and ownership of the proj- cesses. The structural cause of landslide ect, and demonstration of the combined risk in many vulnerable urban communities skills of the government team. Savings in is the absence of regulation regarding con- terms of avoided losses to the community struction, infrastructure, and land use, and costs to the government were also esti- resulting in increased exposure to land- mated. Decision makers require such evi- slides and increased landslide hazard. dence in order to endorse expenditure on Changes in the natural stability conditions landslide risk reduction and to adopt ex of slopes are mainly a consequence of ante policies. changes in natural slope form, drainage, loading, and surface cover. In urban set- tings, the dominant destabilizing factors CONTEXT FOR MoSSaiC can often be attributed to insufficient drain- age and sanitation infrastructure, cutting The MoSSaiC approach was researched and and filling of slope material, removal of veg- developed in a selection of Eastern Caribbean etation, and high-density construction of small island developing states with the sup- houses. Therefore, from a public policy per- port and funding of governments and interna- spective, landslide risk management is tional development agencies. Implementation strongly linked to the feasibility of address- of the hazard reduction measures was under- ing these unauthorized conditions in a taken by government agencies and community politically, financially, and technically coor- residents in conjunction with contractors dinated manner. If a coordinated strategy is from the community. adopted, the appropriate community-based This book offers a flexible blueprint for landslide mitigation works can be imple- countries that want to use the MoSSaiC mented in accord with other policies to approach to reduce landslide risk in communi- address both the immediate and underlying x x i i   P R E FAC E causes of the landslide risk. However, if an can often be reduced in vulnerable urban ad hoc approach to landslide mitigation is communities in the developing world taken, the root causes of the landslide prob- • To provide practical guidance for those in lem may remain. This can result in ineffi- charge of delivering MoSSaiC on the cient, unsustainable projects that create a ground. false sense of security, provide incentives for new unauthorized occupation, bring In reflecting on and seeking to communi- conflicts into communities and/or with the cate our experience of landslide hazard miti- government, and potentially lose any short- gation, this is neither a conventional policy term landslide risk reduction benefits over book nor an explicit field manual. the medium and long term. The purpose of the book is to take readers into the most vulnerable communities in order • There are large numbers of cities in the to understand and address rainfall-triggered humid tropics with very similar problems, landslide hazards in these areas. Community but that are very different in terms of the residents are not just seen as those at risk, but spatial scale to which MoSSaiC projects as the people with the best practical knowl- have, to date, been implemented. The same edge of the slopes in their neighborhood. As problem (vulnerable communities at risk used here, “community basedâ€? means engag- from landslides) in medium or large cities is ing and working with communities to find and likely to require that the approach to land- deliver solutions to landslide risk together. slide mitigation be adjusted to reflect This approach leads governments to develop broader issues. For instance, in larger cities new practices and policies for tackling land- (those whose populations exceed 1 million), slide risk. disaster risk management policies are typi- The book is directed at those responsible cally more complex and demand strategic for initiating, delivering, and sustaining integration and consideration in the con- MoSSaiC in a particular country or city: text of wider development policies. This does not mean that communities do not • Funders and policy makers, typically gov- play a key role in delivering the solution, ernment officials and international devel- but rather that their vision and understand- opment agency staff ing of landslide risk are not unique ele- • MoSSaiC core unit (MCU) personnel ments in the process. (MoSSaiC project managers), typically senior government personnel responsible Success of community-based disaster risk for managing government agencies, depart- management programs is conditioned by local ments, or projects; and leading local experts cultural and social systems. Arguably this is in disaster risk management, landslide haz- best undertaken through careful learning by ard assessment, and community develop- doing, as opposed to a wholesale application of ment best practices from projects that were success- ful in other contexts (Mansuri and Rao 2003). • Government task teams, comprising experts and practitioners responsible for designing and implementing physical ABOUT THIS BOOK works or directly coordinating with com- munities; these are typically engineers, This book has two main aims: community development workers, and technical staff • To demonstrate to international develop- ment agencies, governments, policy mak- • Community task teams with responsibili- ers, project managers, practitioners, and ties at the community level; these are typi- community residents that landslide hazard cally comprised of community residents, CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   x x i i i community representatives, and commu- respective benefits of low and high levels of nity-based contractors. process standardization: • Low levels of standardization can promote In addressing these four audiences, the motivation of those charged with delivering book is intended to the project and adaptation to local issues, • assist in securing the political will to under- but can jeopardize the consistency and take community-based landslide risk reduc- quality of risk reduction measures. tion, • High levels of standardization can promote • illustrate how that objective might be real- high levels of quality and speed of delivery, ized by engaging the community, but can suppress innovation and lead to inflexibility in the local context. • provide a scientific grounding in landslide hazard processes and solutions, • demonstrate the steps involved in on-the- ORGANIZATION AND CONTENTS ground delivery, and OF THIS BOOK • emphasize the importance of evaluating The book’s nine chapters provide guidance to project outcomes. project managers and practitioners on the To these ends, the book contains several entire end-to-end process of community- standard sections in each chapter: based landslide risk reduction. While certain chapters are more directly relevant to one • The “Getting startedâ€? section is aimed at audience than another, it is helpful for all audi- helping the reader quickly and clearly ences to read the “Getting startedâ€? section of understand the chapter’s rationale and how each chapter and be alerted to the nine project to apply MoSSaiC to the local context. milestones. The shared knowledge of mile- • Guiding principles associated with each of stones assists in achieving project ownership the major activities of the program help the and encourages the likelihood of successful policy maker, project manager, or practitio- project continuity, implementation, and post- ner advocate for the methodology with project outcome assessment. stakeholders and demonstrate the central Policy makers and MoSSaiC project manag- role played by community residents. ers should note that chapters 1 (MoSSaiC foundations), 2 (project inception), 4 (com- • The capacity assessment exercise (chap- munity selection), and 9 (project evaluation) ters 2–9) enables the MoSSaiC blueprint to give guidance in areas that predominantly fall be adapted depending on institutional within the remit of policy makers to ensure the structures, protocols, strengths, and weak- existence of a suitable framework. However, it nesses; the nature of the communities; local may fall to project managers to alert the rele- construction practices; and the degree to vant policy maker if local policies are incom- which the local context allows replication plete or require refinement in order to fully of MoSSaiC. allow project implementation. This book standardizes those elements of An overview of the book follows. MoSSaiC that have led to its successful imple- mentation in the Eastern Caribbean, and that Chapter 1. Foundations: Reducing are essential to the overall objectives (such as Landslide Risk in Communities community engagement, mapping localized slope features, and broad drainage design The more socially, economically, and physically principles). In providing a flexible blueprint vulnerable people are, the more disastrous a for MoSSaiC, this book aims to balance the landslide event will be. While there is growing x x i v   P R E FAC E recognition of the increased occurrence of nat- Chapter 2. Project Inception: Teams and ural disasters, there is equal recognition of the Steps lack of on-the-ground implementation of ex ante landslide risk reduction measures. This chapter provides guidelines for the for- This chapter provides an introduction to mation of the MCU which will manage the the MoSSaiC approach, which is focused on project, and of the task teams of practitioners delivering landslide risk reduction measures who will be responsible for project implemen- in vulnerable urban communities in develop- tation. The typical project steps, roles, and ing countries. Specifically, MoSSaiC identifies responsibilities are illustrated. While this pro- and, where appropriate, addresses some of the cess of configuring the teams and project steps physical causes of landslide hazard. may be led by policy makers, established proj- The chapter’s aim is to both inform the ect managers and expert practitioners may reader of the context within which the provide significant assistance. MoSSaiC approach is designed to work and to To achieve the MoSSaiC vision of laying impart something of the vision behind the sustainable foundations for community-based approach. The message is that the rainfall- landslide risk reduction, project managers will triggered landslide hazard faced by the poor- need to est urban communities can often be reduced • build local capacity in the broad area of using relatively simple measures—namely, the landslide hazard reduction while seeking construction of surface drains in appropriate cost-effective solutions; locations. This can be achieved if there is cooperation between government technicians • identify community projects that can be and community residents; hands-on applica- undertaken by existing government-based tion of science and local knowledge; and pro- staff and local communities; and active support from managers, politicians, and • establish team structures to deliver the donor agencies. vision: an MCU that can develop and com- In introducing MoSSaiC, the chapter pro- municate the vision, and task teams to vides the following: develop project strategies and implement • A framework for understanding disaster specific project steps. risk and, more specifically, landslide risk To deliver landslide risk reduction mea- • An overview of trends and lessons learned sures in vulnerable communities requires the in disaster risk management coordination of a diverse team including com- munity residents, field and mapping techni- • Advocacy for taking a proactive approach to cians, landslide experts, engineers, contrac- tackling landslide risk in communities tors, and social development practitioners. • An introduction to MoSSaiC and who This calls for a strong multidisciplinary MCU should be involved to configure and manage specific project steps, roles, and responsibilities. • An overview of how to start a MoSSaiC landslide risk reduction project. Milestone 2: MoSSaiC core unit formed; key responsibilities agreed on and defined This chapter should be read by all stake- holders and should be used by practitioners, project managers, and policy makers alike Chapter 3. Understanding Landslide when explaining the project basis and advo- Hazard cating the MoSSaiC methodology. This chapter provides project managers and Milestone 1: Key catalytic staff briefed on practitioners with an introduction to landslide MoSSaiC methodology processes and illustrates ways of analyzing CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   x x v landslide hazard. A core feature of the Chapter 4. Selecting Communities MoSSaiC approach is that it seeks to ensure that all those participating in the program This chapter describes the community selec- have as clear an understanding of the funda- tion process and provides a framework for mental science of landslide processes as pos- identifying areas where slopes are susceptible sible. Shared technical understanding encour- to landslides, the exposure and vulnerability of ages ownership of landslide mitigation communities to these potential landslide solutions by both government and community. events, and hence the overall landslide risk. The first step in the management of land- The aim is to develop a prioritized list of com- slide risk is to define the scope of the project munities for the implementation of landslide and correctly identify the form of the landslide hazard reduction measures using the MoSSaiC risk. The landslide risk reduction and manage- approach. ment process will only be successful if land- Policy makers and project managers need slides are understood in terms of their under- to coordinate on community selection to lying mechanisms and triggers. ensure that there is a transparent process the Understanding landslide processes and MCU can endorse. Failure in this regard can potential triggering mechanisms lead to unintended consequences such as non- selected communities seeking political • ensures that any landslide risk assessment redress, vocal individuals being given a plat- is scientifically informed, form to promote related agendas, and in • ensures that any proposed landslide hazard extreme cases, the demotivation of the MCU management strategies are appropriate to due to the lack of a robust decision-making the specific local landslide hazard, process. This chapter is designed to help the MCU avoid these issues to the extent possible. • determines if a MoSSaiC-style drainage The sophistication of the methods used will intervention will actually address the land- depend on local data and software availability, slide hazard, and the level of expertise of the government • increases the ability of those implementing task team involved. Practitioners with knowl- the project to justify the landslide hazard edge of local landslide issues, of digital map- reduction measures, ping methods, or of assessing community vul- nerability will be able to provide valuable • helps build confidence within the commu- guidance in this task. The outputs could range nity that the fundamental causes of the from a simple prioritized list of communities landslide hazard are being tackled, and to a detailed landslide risk map for a region or • encourages a holistic and strategic approach country. Whatever the method used, commu- to delivering effective landslide hazard nity selection should be justifiable in terms of reduction measures. the science and rationale underpinning the landslide susceptibility assessment and vul- The content of this chapter is designed to nerability of the communities. be accessible to policy makers, project manag- After the communities have been selected, ers, practitioners, community contractors, and the mapping task team seeks to assemble the community members; however, it is likely to most detailed maps available for these com- be project managers and expert practitioners munities. These maps form the basis for the who take the lead in communicating the sci- community-based landslide hazard and ence. drainage mapping exercise described in chapter 5. Milestone 3: Presentation made to MoSSaiC teams on landslide processes and slope stability Milestone 4: Process for community selection software agreed upon and communities selected x x v i   P R E FAC E Chapter 5. Community-Based Mapping the mapping process. This helps create com- for Landslide Hazard Assessment munity ownership and gives recognition to the fact that residents can be involved in the This chapter provides guidance on the com- immediate solutions to landslide risk and lon- munity-based process to map localized slope ger-term improvement in slope management stability features and identify the dominant practices. causes of the landslide hazard in different Milestone 5: Sign-off on prioritized zones and zones of the slope. This is a central chapter for initial drainage plan project managers and practitioners in the fields of mapping, community development, and engineering. The construction of such a Chapter 6. Design and Good Practice for community slope feature map and subsequent Slope Drainage slope process zone map is the basis for assess- ing whether interventions that manage sur- This chapter is concerned with the detailed face water would be likely to reduce the land- design of drains and other surface water man- slide hazard. Quantitative methods are agement strategies in communities where sur- introduced that can be used to investigate the face water has been identified as the main con- physical slope stability processes and confirm tributor to landslide hazard. The aim is to the landslide hazard and effective solutions. design an integrated drainage intervention The final stage described in this chapter is the plan against a fixed budget that has been production of an initial drainage plan and approved by all stakeholders. intervention prioritization matrix for the com- The products of the community-based munity. mapping process detailed in chapter 5 are a Community members need to be fully community slope feature map, a slope process engaged in the mapping process, not just as zone map identifying relative landslide haz- providers of the information, but as active par- ard, and an initial drainage plan. Having iden- ticipants in the development of the maps. The tified surface water management as an appro- motivation for community member engage- priate measure for landslide hazard reduction, ment at this level will vary locally. In some government engineers and technicians should cases, there will already be formal community find the steps outlined in this chapter helpful groups able to mobilize the rest of the commu- in developing the final drain alignments and nity; in others, policy makers and project man- detailed construction specifications. agers may need to take a much more active Project managers and engineers will find role in establishing suitable frameworks and useful resources and methods for estimating approaches to facilitate community engage- surface water and household water discharge ment. into drains, designing the alignment and The contents of this chapter are primarily dimensions of drains, and estimating con- directed to the project manager and those struction costs. team members with engineering or other Milestone 6: Sign-off on final drainage plan technical expertise; however, it is expected that key community members would use this chapter to develop local awareness of urban Chapter 7. Implementing the Planned landslide processes and acquire landslide haz- Works ard mapping skills. The chapter emphasizes that community- This chapter outlines the major issues to be based slope stability mapping is a central ele- addressed when undertaking drain construc- ment of the MoSSaiC program. As such, it is tion. The aim is to provide guidance on the con- important that the project manager, in partic- tracting process (tendering and letting of con- ular, ensures that all residents participate in tracts to community contractors), construction CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   x x v i i (implementing the works and good construc- munication and capacity-building methods, in tion practice), and the need to achieve high order to guide the development of locally rel- quality in both (supervision of works is central evant strategies. This chapter gives an indica- to project success). Project managers and prac- tion of some such approaches that have been titioners in charge of construction should use used for MoSSaiC programs. and adapt these resources to local practices and Guidance is provided on who should be told standards and ensure good-quality works. what and when—identifying and understand- The proposed drainage plan agreed upon in ing project audiences, developing appropriate chapter 6 is the document that forms the basis project messages, and using different forms of for all the activities relating to the construc- communication. Formal and informal dialogue tion and delivery of the intervention outlined and community participation are emphasized in this chapter. as the basis for communication throughout the The construction phase of the project is of project. Ways of building local capacity are particular interest to policy makers, project identified for different stakeholder groups, managers, practitioners, community mem- and learning by doing is highlighted as a fun- bers, and the media. It is the point of project damental part of the MoSSaiC capacity-build- delivery as far as construction of landslide ing process. hazard reduction measures is concerned. See- ing that this process is successfully managed Milestone 8: Communication and capacity- within time and budgetary constraints not building strategies agreed upon and only maximizes the likelihood of sound con- implemented struction but also lays the foundation for com- munity ownership postcompletion. A success- Chapter 9. Project Evaluation fully managed project enhances the likelihood of the community becoming a powerful advo- This chapter stresses the importance of evalu- cate for additional interventions and of influ- ating project outputs and outcomes. It pro- encing future policy. Poor construction and vides a rationale for undertaking an evaluation subsequent rejection of the intervention by the and a blueprint for an evaluation strategy. community has the reverse effect—and the Monitoring and evaluation are widely spo- potential of making landslide and flooding ken of in the context of project management, issues worse. This chapter provides guidance yet in many disaster risk reduction initiatives on how to run the implementation process in adequate baseline data are not collected. Con- recognition of these potential challenges. sequently, it can be difficult to find adequate Milestone 7: Sign-off on completed measures of success on which a project may be construction evaluated after just two or three years post- project. This in turn gives rise to the recogni- tion that longer-term project impact evalua- Chapter 8. Encouraging Behavioral tions are rarely, if ever, instigated (Benson and Change Twigg 2004). Landslide risk reduction evi- dence faces the challenge of counterfactual This chapter is concerned with developing analysis—how to demonstrate conclusively communication and capacity-building strate- what would have happened if a different action gies that encourage the adoption of good land- had been taken. slide hazard reduction practices and policies The MCU should therefore understand and by communities and governments. communicate the following: The strategies that work best are likely to be highly dependent on local situations. The aim • The need to secure relevant data both dur- of this chapter is to review behavior change ing and after the project to support project processes and principles, and potential com- impact x x v i i i   P R E FAC E • How the immediate benefits (outputs) and governance of the MoSSaiC project manage- longer-term benefits (outcomes) relate to ment structure. the overall program objectives You may be responsible for working with • That delivering effective landslide hazard MoSSaiC project managers and managing reduction measures provides evidence that their reporting line to the government. This ex ante landslide risk reduction can both book provides guidance on how to undertake work and pay. that process, evidence of what has worked, and information on options to consider. This evidence base is important if the per- Of the entire delivery process, chapters 1 ceptions, practices, and policies of individuals, (MoSSaiC foundations), 2 (project inception), governments, and international funding agen- 4 (community selection), and 9 (project evalu- cies are to be changed regarding community- ation) are perhaps the most significant in pol- based landslide risk reduction. icy terms. They represent areas that demand clear policy frameworks within which the Milestone 9: Evaluation framework agreed upon more technical aspects of mitigation measure and implemented delivery can be undertaken. Lack of clarity in these areas can lead to inefficiency, delay, and failure to align stakeholder expectations. HOW TO USE THIS BOOK Funders and policy makers play a key role in promoting structures that guide the transfer Note to funders and policy makers of project funds to the relevant implementing and community agencies in an efficient and It is important to provide a context when timely manner. Project funds are finite, and advocating for policy change. Globally, the governments can therefore fund only limited amount of aid given to the developing world is construction efforts. Funders and policy mak- increasing and represents only a small fraction ers can seek to ensure that policies are in place of that needed with regard to natural disasters to harmonize disaster risk reduction expendi- (Mills 2004)—the number of which continues ture arising from different sources within a to rise despite efforts to date. Mitigation mea- single community. sures are widely recommended but rarely Funders and policy makers can encourage implemented (Holmes 2008) because the ben- the use of this book within government and by efits are not tangible; they are disasters that other national agencies, nongovernmental did not happen. Not surprisingly, there is clear organizations, and civil society organizations evidence of the continued accumulation of to communicate the vision of community- urban disaster risk (Bull-Kamanga et al. 2003), based landslide risk reduction and to encour- driven largely by the speed of societal change, age feedback so as to further refine the as the vulnerable move to urban areas, the hill- approach and provide additional content. You sides of which are so often already prone to thus have an important role in creating a cul- landslides. Thus, as Yunus (2011) comments, ture of commitment and delivery efficiency, “The more time spent with poor people, the and ultimately in driving changes in ex ante more one realizes that their circumstances are landslide risk mitigation practice and policy. dictated by the systems society has con- structed.â€? Note to the MoSSaiC core unit As a funder or policy maker, you should anticipate various stakeholder interests aris- The MoSSaiC process begins with a series of ing within community-based interventions. decisions that have to be made almost immedi- Issues that might need to be reconciled include ately to configure the MCU (the project man- political priorities, seeking objectivity in com- agement team). MCU personnel typically com- munity selection, landowner interests, and prise senior government personnel responsible CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   x x i x for managing government agencies, depart- If you are a task team leader, you will need ments, or projects; and/or with expertise in a to work closely with the MCU to adapt each particular field such as disaster risk manage- project step according to local capacity, ensure ment, landslide hazard assessment, engineer- that the tasks required to complete each step ing, or community development. are appropriately assigned to a task team, and Your role as a MoSSaiC project manager or identify and build your team. As a practitio- expert advisor means that you should be ner—and since this book is a blueprint—you familiar with the entire contents of this book. will be responsible for capturing and incorpo- You will be responsible for implementing the rating local good practice insofar as it relates policy decisions and for ensuring delivery of to your area of expertise and the MoSSaiC the appropriate measures on the ground in methodology. Under the guidance of the MCU, communities. You will need to apply the you will be responsible for implementing spe- resources in this book according to local fac- cific project steps and tasks, and for ensuring tors. delivery of the appropriate landslide mitiga- Replication should not be considered an tion measures on the ground in communities. automatic process. Sometimes things work for idiosyncratic reasons—a charismatic and liter- Note to community task teams ally irreplaceable leader or a particular and unrepeatable crisis that solidifies support for a Community task teams comprise community politically difficult innovation. One-time suc- residents and those with responsibilities at the cesses thus may not be replicable (World Bank community level, such as community repre- 2004, 108). sentatives and community-based contractors. This book explains the project steps, teams, Community residents are the most critical and supervision levels that are necessary to partners in the program; they are deliver appropriate construction of hazard • participants in the entire process, reduction measures on the ground. It empha- sizes the importance of basing the entire pro- • those to whom the initiative is directed, gram in the community. It provides a logical • those who will “ownâ€? the implementation description of how to configure teams and long after construction has finished, design physical measures to reduce landslide hazard in vulnerable communities. The book • an important source of knowledge of local does not tell you exactly what to do, but it slope stability and drainage features in the should improve the likelihood of good project community, and outcomes and of delivering a strategic and • catalytic in making the project happen. holistic community-based landslide risk reduction program. Managing and delivering Each chapter begins with a “Getting community-based projects is hard work, but startedâ€? section; these are intended to provide working with the community empowers both an accessible overview to allow communities residents and government teams to contribute to understand key project concepts. If you are their knowledge and skills. a community representative, you may find it helpful to read these in depth. Other particu- Note to government task teams larly relevant book sections to refer to are chapter 5, which describes the community- Government task teams (typically government based mapping process; and chapter 8, which engineers, community development workers, provides guidance on formal and informal and technical staff ) are responsible for spe- community meetings, written and visual cific tasks related to implementing physical resources (e.g., leaflets and posters), and the works on the ground or directly coordinating use of the media. You will need to work with with communities. the government task teams to understand and x x x   P R E FAC E communicate important project messages to process. You may also have the opportunity to community residents and facilitate their par- use your skills in the design and construction ticipation. You should also help the govern- of landslide mitigation measures (see sections ment task teams understand the community 6.4 and 6.5 on drain design, and sections 7.5–7.8 context. on good drain construction practices). If you are a construction contractor or a worker living in a community where MoSSaiC Helpful questions is being implemented, you will have specialist local knowledge that is vital to the success of Table P.1 presents some typical questions the project. You may have useful information about MoSSaiC and where guidance can be to share during the community-based mapping found in this book. TAB L E P.1  Critical questions and decisions addressed in this book CRITICAL QUESTION/DECISION WHERE TO LOOK FOR HELP Why should landslide risk reduction be community based? Chapter 1. Foundations: What are the unique features of the MoSSaiC approach? Reducing Landslide Risk in Where can MoSSaiC be applied? Communities What teams are needed? Chapter 2. Project Inception: What are the project steps? Teams and Steps What are the roles and responsibilities of the teams? What forms of slope failure does the MoSSaiC approach address? Chapter 3. Understanding What is the relevant spatial scale for MoSSaiC interventions? Landslide Hazard How is landslide hazard assessed? How can the most landslide-prone areas be identified? Chapter 4. Selecting How can the most vulnerable communities be identified? Communities How are communities selected for a MoSSaiC intervention? How can landslide hazard be mapped in a community? Chapter 5. Community- How effective will surface water management be in reducing the landslide hazard? Based Mapping for Landslide How is the initial drainage plan developed? Hazard Assessment Where should drains be built to improve slope stability? How can surface water runoff, household gray water discharge, and required drain sizes be Chapter 6. Design and Good estimated? Practice for Slope Drainage What are the most appropriate types of drain design and construction? What construction practices should be promoted? Chapter 7. Implementing the Why is site supervision so important? Planned Works How do communities and governments adopt new landslide mitigation practices and policies? Chapter 8. Encouraging What are the components of a communication strategy? Behavioral Change What are the components of a capacity-building strategy? How can landslide risk reduction measures be evaluated? What are the MoSSaiC key performance indicators? Chapter 9. Project Evaluation What evidence is needed to support ex ante landslide mitigation policies? Where can additional resources be found? At the end of each chapter CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   x x x i REFERENCES Mansuri, G., and V. Rao. 2003. Evaluating Community-Based and Community-Driven Development: A Critical Review of the Evidence. Benson, C., and J. Twigg. 2004. “Measuring Development Research Group. Washington, Mitigation Methodologies for Assessing Natural DC: World Bank. Hazard Risks and the Net Benefits of Mitigation—A Scoping Study.â€? ProVention Mills, E. 2004. “Insurance in a Climate of Change.â€? Consortium, Geneva. Science 309 (5737): 1040–44. Bull-Kamanga, L., K. Diagne, A. Lavell, E. Leon, F. —. 2004. Making Services Work for Poor People. Lerise, H. MacGregor, A. Maskrey, M. Meshack, World Development Report. Washington, DC: M. Pelling, H. Reid, D. Satterthwaite, World Bank. J. Songsore, K. Westgate, and A. Yitambe. 2003. Yunus, M. 2011. Blog post August 28. https://plus. “From Everyday Hazards to Disasters: The google.com/114848435876861502546/ Accumulation of Risk in Urban Areas.â€? posts/9SwwVFedo9P. Environment and Urbanization 15 (1): 193–203. Holmes, J. 2008. “More Help Now Please.â€? The Economist November 19. x x x i i   P R E FAC E Acknowledgments This book was written while the authors were under the supervision of Patricia Katayama, working in the Latin America and the Carib- Andrés Meneses, and Dina Towbin; and Nita bean Disaster Risk Management team at the Congress undertook copyediting, typesetting, World Bank, Washington, D.C. Colleagues in and proofreading of the manuscript. that team deserve our thanks for supporting This book is based on a community-focused and resourcing our continued commitment to approach and has involved the authors spend- deliver MoSSaiC (Management of Slope Sta- ing many months working in communities bility in Communities) to communities more with residents who are among the most vul- widely in the region and beyond. nerable. We are grateful to members of com- In particular, we thank Francis Ghesquiere munities in Bequia, Dominica, St. Lucia, and and Niels Holm-Nielsen for their continued St. Vincent and the Grenadines with whom we support of initiatives that led to this book. Dis- have spent so much time, and from whom we cussions with other World Bank team mem- have learned so much. We especially acknowl- bers, including Joaquin Toro, Maricarman edge the support and friendship of Robert Esquivel, Tiguist Fisseha, and Rossella Della Charles, McArthur Edwards, and Ruben Leon Monica were enormously helpful throughout. in St. Lucia. Review comments received from colleagues Our vision for MoSSaiC would not have in the Latin America and the Caribbean been realized had it not received support from Region's Disaster Risk Management and Calixte George, Ignatius Jean, and Kenny Urban Unit and Water Supply and Sanitation Anthony as then-members of the government Unit at the World Bank, Washington, D.C., of St. Lucia. Equally accepting of the vision, Kirk Frankson (Office of Disaster Prepared- Donovan Williams, then-Director of the Pov- ness and Emergency Management, Jamaica), erty Reduction Fund in St. Lucia, facilitated us Chamberlain Emmanuel (government of St. in undertaking a pilot program in St. Lucia. Lucia), Abhas K. Jha (East Asia and Pacific This support was continued by his successor, Infrastructure Unit, World Bank) and M. Yaa Joachim Henry. We acknowledge with thanks Pokua Afriyie Oppong (Social Development the technical support for program delivery we Department, World Bank), as part of the World have received from government of St. Lucia Bank review process chaired by Francis Ghes- personnel: David Alphonse, Chamberlain quiere, are acknowledged with grateful thanks. Emmanuel, Peter Gustave, and Cheryl The Office of the Publisher provided edito- Mathurin. Within the Eastern Caribbean sub- rial, design, composition, and printing services region, David Popo of the Organisation of East- xxxiii ern Caribbean States helped facilitate pilot Funding for the work undertaken by the projects in Dominica and St. Vincent and the authors that provided the context for much of Grenadines. this book was provided by the World Bank, the During our time working overseas in com- governments of St. Lucia and Dominica, the munities and in writing this book in Washing- United Nations Development Programme, the ton, D.C., and Bristol, United Kingdom, we U.S. Agency for International Development, received support from many colleagues at the the University of Bristol, SETsquared Partner- University of Bristol, especially Neil Bradshaw ship UK, and the British High Commission, St. and Eric Thomas. Lucia. x x x i v   A C K N O W L E D G M E N T S About the Authors Malcolm Anderson is Visiting Fellow at Elizabeth Holcombe holds a PhD and an Brasenose College and Visiting Professor of MSci from the University of Bristol, where Hydrology at the University of Oxford, a she is a Lecturer in Civil Engineering. She is a Senior Landslide Risk Management Specialist Landslide Risk Management Specialist Con- Consultant in the World Bank’s Latin America sultant in the World Bank’s Latin America and the Caribbean Disaster Risk Management and the Caribbean Disaster Risk Manage- Team in Washington, D.C., and Professor at ment Team in Washington, D.C. Her back- the University of Bristol, United Kingdom, ground is in environmental science and the where he was Pro Vice-Chancellor (Research) numerical modeling of hillslope hydrology from 2005 to 2009. He holds a PhD from the and stability. She has had extensive overseas University of Cambridge, and was elected to a experience in research, project management, Research Fellowship at Sidney Sussex Col- and implementation of landslide risk reduc- lege, Cambridge. He is the author of over 200 tion projects in vulnerable communities in papers, as well as of industry standard soft- the Eastern Caribbean. She has presented ware, and Founder and Editor-in-Chief of the invited papers at international conferences in journal Hydrological Processes. He has worked the Caribbean, Europe, and the Far East, and on many government research projects world- is the author of numerous papers and book wide, principally in the Far East (Hong Kong chapters in the field of landslide risk reduc- SAR, China; Indonesia; and Malaysia), the tion. Her research on MoSSaiC was high- United States, and the Caribbean. He is an lighted in the 2010 World Development Report elected Fellow of the Institution of Civil Engi- and profiled at the Aid Effectiveness Show- neers, London, and was a Council Member of case hosted at the World Bank in 2011. She the U.K. Natural Environment Research received the 2007 Trevithick Award from the Council (2001–07), and a Board Member of Institution of Civil Engineers, London, and the U.K. Engineering and Physical Sciences managed the team that was awarded the Research Council’s Technology Strategy Grand Prize at the 2010 Random Hacks of Board (2009–11). Kindness hackathon in Washington, D.C. xxxv Disclaimer The material in this book is • information of a general nature only that is not intended to address the specific circumstances of any particular project or application; • not necessarily comprehensive, complete, accurate, or up to date; and • not professional or legal advice—if specific advice is needed, a suitably qualified professional should be consulted. It follows that none of the individual contributors, authors, developers, or sponsors of this book, nor anyone else connected to it, can take any responsibility for the results or consequences of any use or adoption of any of the materials or information presented within this book. To the fullest extent permitted by law, the authors accept no responsibility for any loss or damage, which may arise from reliance on the guidance, materials or information contained within this book. Abbreviations cf cubic foot CHASM Combined Hydrology and Slope Stability Model DRM disaster risk management DRR disaster risk reduction ft foot gal gallon GDP gross domestic product GIS geographic information system GPS global positioning system h hour in inch km kilometer kPa kilopascal KPI key performance indicator L liter m meter MCU MoSSaiC core unit min minute mm millimeter MoSSaiC Management of Slope Stability in Communities NGO nongovernmental organization RFT request for tender SAR special administrative region s second SIDS small island developing states UN United Nations All dollar amounts are U.S. dollars unless otherwise indicated. xxxvii “We’re still to some extent sleepwalking our way into disasters for the future which we know are going to happen, and not enough is being done to mitigate the damage.â€? —John Holmes, UN Under-Secretary-General for Humanitarian Affairs (Lynn 2009) CHAPTER 1 Foundations: Reducing Landslide Risk in Communities 1.1 KEY CHAPTER ELEMENTS 1.1.1 Coverage This chapter outlines the foundations for tion measures in vulnerable communities. The delivery of MoSSaiC (Management of Slope listed groups should read the indicated chap- Stability in Communities) landslide risk reduc- ter sections. AUDIENCE CHAPTER F M G C LEARNING SECTION     MoSSaiC vision and rationale 1.2    Trends in disaster and landslide risk; components of disaster risk management 1.3    MoSSaiC foundations: scientific basis, community base, and evidence base 1.4    MoSSaiC components: book structure and chapter outputs 1.4.5    How to start a MoSSaiC project and who to brief 1.5 F = funders and policy makers  M = MoSSaiC core unit: government project managers and experts  G = government task teams: experts and practitioners  C = community task teams: residents, leaders, contractors 1.1.2 Documents CHAPTER DOCUMENT TO BE PRODUCED SECTION List of senior policy makers who will champion and endorse the project 1.2; 1.5.2 List of staff to be considered for inclusion in the MoSSaiC core unit 1.5.2 1 1.1.3 Steps and outputs STEP OUTPUT 1. Understand the disaster risk context with respect to landslides Relevance of 2. Understand the innovative features and foundations of MoSSaiC MoSSaiC approach to local landslide risk 3. Identify general in-house expertise and the appropriate institutional struc- context identified tures for codifying a local approach toward landslide risk reduction 4. Brief key individuals on MoSSaiC (politicians, relevant ministries, in-house Core unit of team experts) members identified 1.1.4 Community-based aspects ics. Rapid urbanization and the associated growth of unauthorized and densely popu- The chapter introduces MoSSaiC as an inte- lated communities in hazardous locations grated method for engaging policy makers, (such as steep slopes) are powerful drivers in a project managers, practitioners, and vulnera- cycle of disaster risk accumulation. Frequently, ble communities in reducing urban landslide it is the most socioeconomically vulnerable risk in developing countries. Community resi- who inhabit marginal landslide-prone slopes— dents are not just seen as those at risk, but as thus increasing their exposure to landslide the people with the best practical knowledge hazards and often increasing the hazard itself. of the slopes in their area. By engaging and The more socially, economically, and physi- working with communities to find and deliver cally vulnerable people are, the more disas- solutions to landslide risk, governments will trous a landslide event will be. While recogni- develop new practices and policies. tion is growing of the increased occurrence of landslide disasters, there is equal recognition that on-the-ground implementation of land- 1.2 GETTING STARTED slide risk reduction measures is lacking. MoSSaiC aims to address these issues. Its 1.2.1 Briefing note key premises follow. A practical approach to reducing landslide risk • Disaster risk mitigation pays, and invest- ment in reducing rainfall-triggered land- In introducing MoSSaiC, the chapter provides slide hazards in vulnerable communities • a framework for understanding disaster can often be justified. risk, specifically landslide risk; • Engaging existing government expertise • an overview of recent influences on disaster for implementing risk reduction measures risk management (DRM); can build capacity, embed good practice, and change policy. • advocacy for a proactive approach in tack- ling landslide risk in communities; • Ensuring community engagement from start to finish can establish ownership of • an introduction to MoSSaiC’s three founda- solutions. tions; and Specifically, construction of relatively sim- • an overview on starting a MoSSaiC land- ple measures such as surface water drains can slide risk reduction project. often improve slope stability, reduce the land- Many areas of the world are at risk from slide risk to communities, and reduce future landslides and their consequences (figure 1.1). disaster management costs to governments. Rainfall-triggered landslides particularly Landslide mitigation can be achieved through affect developing countries in the humid trop- cooperation between government technicians 2    C H A P T E R 1 .   F O U N DAT I O N S : R E D U C I N G L A N D S L I D E R I S K I N CO M M U N I T I E S FI G U R E 1.1  Global landslide risk Landslide risk slight moderate severe Source: National Aeronautics and Space Administration (NASA) map adapted from Hong, Adler, and Huffman 2006. Note: NASA scientists assembled the risk map from topographic data, land cover classifications, and soil types. Black dots identify the locations of landslides that occurred from 2003 to 2006. Light blue indicates areas of low risk; purple and dark red indicate areas at the highest risk. and community residents; hands-on applica- —— Scientific methods are used to justify tion of science and local knowledge; and pro- solutions to both communities and gov- active support from managers, politicians, and ernments. donor agencies. • Foundation 2: MoSSaiC is community MoSSaiC vision and foundations based. The MoSSaiC vision is to lay sustainable foun- —— Community residents are engaged in dations for community-based landslide risk identifying landslide risk causes and reduction. These foundations are a scientific solutions. basis for reducing landslide hazard, a commu- —— Contractors and workers from the com- nity-based approach for delivery of mitiga- munity are employed in constructing tion measures on the ground, and an evidence drainage solutions. base demonstrating that such an investment both pays and works (figure 1.2). —— Government managers and practitioners These foundations govern the way in which form teams with the necessary expertise MoSSaiC should be understood, implemented, to work with communities and deliver and integrated into wider policy and practice. mitigation measures. —— The vision is shared and championed in • Foundation 1: MoSSaiC is science based. communities and by governments. —— Localized physical causes (often poor • Foundation 3: MoSSaiC is evidence based. drainage) of landslide hazard are identi- fied. —— Appropriate physical works are deliv- ered to reduce landslide hazard. —— Appropriate mitigation measures that address the causes of landslide hazard —— The majority of project funding and time are identified and implemented. is spent in the communities. CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   3 F IG U R E 1 . 2  MoSSaiC premises, vision, and foundations PREMISES • Disaster risk mitigation pays, and investment in reducing rainfall-triggered landslide hazards in vulnerable communities can often be justiï¬?ed • Engaging existing government expertise can build capacity, embed good practice, and change policy • Ensuring community engagement from start to ï¬?nish can establish ownership of solutions VISION Sustainable foundations for community-based landslide risk reduction FOUNDATIONS Science based Community based Evidence based —— The cost-effectiveness of landslide risk • Landslides are a community issue. Slope reduction is demonstrated. stability in communities is a community- scale issue in that landslides are spatially —— The benefits of community-based land- discrete events caused by localized slope slide risk reduction are demonstrated so stability mechanisms. Each community and that behavior and policy are changed. the corresponding hillside it occupies will Management and community in MoSSaiC have its own unique landslide hazard and vulnerability profile. Thus, determining MoSSaiC recognizes that landslides are both a how to manage slope stability in a particu- management issue and a community issue. lar community requires application of com- munity knowledge of the slope and scien- • Landslides are a management issue. tific/engineering diagnosis of landslide Actions can be taken to reduce or manage mechanisms at the community scale. This landslide hazards or their consequences. community-based approach continues with Slope stability management must involve the construction of drainage by community communities that may inadvertently be members, and with the support of govern- adding to the risk and will almost certainly ment (table 1.1). Ensuring community be affected by it. This management must engagement from start to finish can estab- also involve governments. A government lish ownership of solutions. can choose to take a proactive approach to landslides in communities by identifying Communicating the vision and establishing and enacting appropriate landslide risk MoSSaiC in your country management policies. Governments will often have experts with the combined skills The vision outlined above and detailed in this necessary for reducing landslide risk in chapter may resonate with certain catalytic communities. Engaging existing govern- individuals in a particular country, be they ment expertise for implementing risk community leaders, engineers, civil servants, reduction measures can build capacity, or politicians. These leaders in turn will need embed good practice, and change policy. to communicate the vision to decision makers 4    C H A P T E R 1 .   F O U N DAT I O N S : R E D U C I N G L A N D S L I D E R I S K I N CO M M U N I T I E S TAB L E 1.1  The key teams and tasks in MoSSaiC TASK Diagnose landslide hazard and Implement physical measures to TEAM design intervention reduce landslide hazard Construct physical measures, Community: residents, Contribute local knowledge of change slope management leaders, and contractors slope, hazard, and vulnerability practices Government: policy makers, Apply in-house scientific, engineer- Issue and supervise contracts, build project managers, and ing, and development expertise in-house capacity practitioners Manage project and teams However, within it, scientific knowledge of and other influential individuals in order to hazards and their effects and technological initiate a MoSSaiC project. alternatives for mitigation take on a com- Government approval is a prerequisite for pletely new meaning, transforming them- initiating MoSSaiC, developing the financial selves into vital instruments at the service of basis for its implementation, and establishing development (Maskrey 1992, 5). a core unit of in-house experts and project managers. Securing government approval Designed as explicitly community based, relies on a clear exposition of MoSSaiC. One of MoSSaiC provides a new method for deliver- the primary functions of this book is to serve as ing landslide risk reduction in the most vul- a resource for this purpose. nerable communities. The combination of fea- Once there is a clear mandate for the estab- tures highlighted below is what makes this lishment of a MoSSaiC project, it is vital to approach unique. engage at-risk communities as early as possi- • It develops sustainable foundations for the ble, set realistic expectations within those delivery of landslide risk reduction mea- communities, and ensure timely project deliv- sures in communities (chapter 1). ery. It is often pragmatic to start small, and then build upon each success as the core unit • It identifies, uses, and builds existing capac- and community adapt the MoSSaiC blueprint ity for risk reduction (chapter 2). to fit the local context. It is easier to embrace a • It identifies the risk drivers so that mitiga- vision if there is evidence of success on the tion measures can be justified (chapter 3). ground. • It provides a method for prioritizing the 1.2.2 What is unique about MoSSaiC? most vulnerable (chapter 4). • Community residents are active partici- Taking an approach focused on community pants throughout the entire process (chap- residents means ter 5). …integrating tasks into a long-term pro- gramme covering all phases of disaster and • It delivers landslide hazard reduction mea- incorporating hazard mitigation into wider sures on the ground (chapter 6). development planning. The methodology of working is necessarily slow, small scale, long • It emphasizes the critical role of site super- term, multidisciplinary, and multisectoral. vision in partnership with community con- Because of its complexity, its incremental tractors (chapter 7). planning, and its dependence on political negotiation, this approach must seem like a • It encourages behavioral change at the recipe for chaos to many experts accustomed community level and within government to working in conventional programs. (chapter 8). CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   5 • It promotes the importance of providing sitating clear communication and a major time evidence of risk reduction achieved (chap- commitment. In the MoSSaiC approach, com- ter 9). munity residents are seen not as passive recip- ients of information, but as agents contribut- 1.2.3 Guiding principles ing both to the landslide hazard and to the solutions. The challenge is to ensure that indi- • Develop a “mitigation mindsetâ€? with respect viduals are major participants at every stage in to urban landslide risk. the process so that everyone can own the proj- • Understand that there is no “one size fits ect. Only in this manner can behavioral change allâ€? solution to landslide risk reduction— be achieved. each country and community will have its Similarly, government field teams, techni- own landslide risk profile. cians, and construction supervisors should be treated as contributors and their extensive • Recognize that there is often something field experience seen as a valuable resource. that can be done to reduce the risk—learn These team members are the interface with from other approaches and adapt the the community. If they are not well informed MoSSaiC blueprint. and involved by their managers, their owner- • Learn the value of community knowledge ship of the project cannot be ensured. and the importance of community involve- Sound project management delivers quality ment throughout. interventions. Conversely, poor management can actually make a landslide problem worse, • Realize that the government may already alienate communities and field teams, result in have the skills and know-how to tackle budget overruns, and prevent the MoSSaiC landslide risk in communities. approach from being established in a country. • Look for key individuals in government and The project management and technical teams communities who see the big picture and are responsible for designing and supervising can drive behavioral change. construction, and for achieving a sufficiently high level of engagement with all stakehold- 1.2.4 Risks and challenges ers, so that the intervention meets the required Getting commitment from all key stakeholders goals, complies with necessary standards and safeguards, and encourages replication. Securing a mandate for MoSSaiC from govern- Securing evidence that risk reduction is working ment is necessary for establishing and manag- ing the requisite teams, procuring services and Many disaster risk reduction (DRR) projects resources, and implementing landslide mitiga- lack analysis of medium-term impacts. The tion measures in communities. The multidis- challenge is to keep project engagement by all ciplinary nature of MoSSaiC means that its stakeholders sufficiently strong so that evi- components may fall between or across the dence of postproject performance is kept, ana- purview of different ministries, or that minis- lyzed, and communicated. Only with such evi- tries may not wish to collaborate. A political dence can policy be changed or existing DRR champion may be able to overcome this, but policy measures reinforced. Evidence of risk energetic individuals from different agencies reduction is also important, since evaluations will also need to join forces. of mitigation measures have to respond to the In addition to requiring top-down govern- counterfactual argument of what would have ment action, MoSSaiC is a bottom-up approach happened in the absence of the intervention. to landslide mitigation and needs to have a Psychological and situational barriers secure grounding in communities. This grounding can only be achieved through sub- There are several reasons why relatively few stantial interaction with communities, neces- people, communities, and governments are 6    C H A P T E R 1 .   F O U N DAT I O N S : R E D U C I N G L A N D S L I D E R I S K I N CO M M U N I T I E S prepared or able to invest in landslide mitiga- their reactions to disasters and may relo- tion measures (Kunreuther, Meyer, and Kerjan cate communities to unsuitable locations. forthcoming): • Lack of risk awareness. Communities may not be aware that they live in a high-land- 1.3 DISASTER RISK: CONTEXT slide-risk area, and governments may not AND CONCEPTS have an adequate basis for identifying the most at-risk communities. 1.3.1 Global disaster risk • Helplessness in the face of landslide risk. This subsection briefly reviews the evidence Communities and governments may be all for the increasing number and consequences too aware of the risk but have little realiza- of disasters caused by natural hazards. It pro- tion of the potential for relatively low-cost, vides both the broad context for DRM and the in-house solutions. specific context for the management of slope stability in communities. • “Samaritan’s dilemma.â€? Communities may avoid investing in good slope manage- Increases in the number of disasters ment practices and risk reduction measures Reports from international development agen- on the assumption that a government (the cies and from the geoscience and engineering “good Samaritanâ€?) will assist them in case communities point to an increase in the occur- of disaster. rence of natural hazards and their conse- • Procrastination. There is a natural ten- quences (figure 1.3), especially with respect to dency to postpone taking actions that countries with low to medium levels of devel- require investments of time and money. opment (AGS 2000; Alcántara-Ayala 2002; UNDP 2004, 2008). See IFRC (2004) for a • Budget constraints. Communities may not comprehensive discussion of this trend. be able to afford to invest in landslide risk This apparent increase has many possible reduction measures. Governments may not explanations (IEG 2006; IFRC 2004), includ- have sufficient understanding of the poten- ing the following: tial solutions and associated benefit-cost ratios, and therefore are unable to justify • Increase in the reporting and recording of the expenditure. disasters. Improved communication and the development of international and local • Short-term planning horizons and hyper- disaster databases have enabled the system- bolic discounting. People in the most vul- atic recording of disasters. nerable communities may be living hand to • Development activities. Construction, mouth and consequently be unwilling to mining, and agriculture affect the natural consider putting money toward low-cost environment and can increase some hydro- slope management solutions that will not meterological hazards (such as landslides, provide for their daily needs. Governments erosion, flooding, and drought). might place more value on projects that show immediate benefits rather than on • Global anthropogenic effects such as cli- investing to offset a future loss that may or mate change. For example, a rise in tropical may not occur. sea temperatures of approximately 1 degree Celsius over the past century may have con- • Learning from failures. People often do tributed to an increase in weather-related not seem to learn from past experiences of disasters. disaster. Following a landslide, people may rebuild their homes in the same or similar • Socioeconomic and environmental driv- location. Governments also tend to repeat ers leading to increased exposure and CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   7 vulnerability. Poverty, drought, and famine catastrophic way, especially in small island can result in people moving to deltas, flood- developing states (SIDS) (World Bank 2010b). plains, the steep slopes on the fringes of For example, Granada lost 200 percent of its urban areas, and other marginal areas GDP to Hurricane Ivan (World Bank 2005a). exposed to natural hazards. Observed trends in disaster risk are not simply a physical phenomenon, but are closely Such evidence further supports arguments related to the process of human development: for DRR that have been advanced in the inter- “the development choices of individuals, com- national development policy community in munities and nations can generate new disas- recent years (DFID 2004; Pelling and Uitto ter riskâ€? (UNDP 2004, 1). Analysis of time- 2001; Twigg 2004). series data has provided insight into the causative factors of the increased losses asso- Increases in the cost of disasters ciated with disasters. A study of mainland U.S. Paralleling the increase in the number of disas- hurricane damage from 1900 to 2005 shows ters has been the rise in their consequences that if damage data are normalized (with 2005 with regard to direct and indirect impacts, and as the datum) with respect to changes in infla- insured and uninsured losses (figure 1.3). It is tion and wealth at the national level, and widely recognized that the incidence and changes in population and housing units at the impact of disasters caused by natural hazards coastal county level, there is no trend in dam- disproportionately affects developing coun- age over time (figure 1.4) (Crompton et al. tries. Numerous studies have documented evi- 2010; Crompton and McAneney 2008; Pielke dence of the human, economic, and environ- et al. 2008). The absence of a trend in normal- mental losses experienced by developing ized loss data suggests that increased observed countries at the local and national levels (e.g., losses are attributable to increases in the num- Charveriat 2000; Rasmussen 2004; UNDP ber of buildings over time; thus, it matters 2004). Such losses can affect the gross domes- greatly what is built, where it is built, and how tic product (GDP) of developing countries in a it is built. FI G U R E 1. 3  Number of great natural catastrophes and associated economic losses worldwide, 1950–2010 a. Number of events with trend b. Overall and insured losses with trend number $, billions 16 250 2 14 200 12 10 150 8 6 100 4 50 2 0 0 1950 1960 1970 1980 1990 2000 2010 1950 1960 1970 1980 1990 2000 2010 climatological events (extreme drought/temperature, forest fires) overall losses (2010 values) hydrological events (floods, mass movements) insured losses (2010 values) meteorological events (storm) trend in overall losses geophysical events (earthquake, tsunami, volcanic eruption) trend in insured losses Source: © Münchener Rückversicherungs-Gesellschaft, Geo Risks Research, NatCatSERVICE 2011. 8    C H A P T E R 1 .   F O U N DAT I O N S : R E D U C I N G L A N D S L I D E R I S K I N CO M M U N I T I E S spatial and temporal scales, affected parties, FI G U R E 1.4  Normalized losses from U.S. and methods of risk assessment and risk man- Gulf and Atlantic hurricane damage, agement. 1900–2005 Studies by regional networks such as La Red $, billions (Latin America) and Periperi (southern Africa) 160 provide evidence that smaller-scale and 140 “everydayâ€? disasters (categories 0–2) have 120 been increasing in developing countries in 100 recent years (Bull-Kamanga et al. 2003). The 80 landslide risk reduction approach described in 60 this book has been built on experiences gener- 40 ally relating to categories 0–2. MoSSaiC may 20 also be applicable to the higher categories of 0 landslide catastrophe. 1905 1925 1945 1965 1985 2005 Source: Pielke et al. 2008. Global landslide risk Note: Data are normalized to 2005 by adjusting for Rainfall-triggered landslides represent a sig- changes in inflation, wealth, and housing units. The black line is an 11-year centered moving average. nificant but underreported threat to lives, property, and development, particularly in Southeast Asia and Latin America and the Recording disasters Caribbean (UNU 2006). Available data indi- To assist in the analysis and management of cate that the majority of fatalities occur in risk, disasters are recorded and categorized by lower-middle- and low-income countries (fig- various agencies. For example, the Emergency ures 1.5 and 1.6), and that in excess of 2 million Events Database (EM-DAT) is maintained by people are exposed to landslide hazards the World Health Organization Collaborating worldwide (UNISDR 2009). However, the full Centre for Research on the Epidemiology of impact of landslides is masked by broader sta- Disasters (CRED). In EM-DAT a disaster is tistics relating to the precipitation events that defined as an event in which 10 or more people trigger them and the concurrent wind damage, are killed, 100 or more are injured, or where floods, and storm surges. For a particular rain- damage is sufficient to call in international fall-triggered disaster, it is possible that “losses agencies (UNDP 2004). Munich Re classifies from landslides may exceed losses from the disaster risk in terms of categories of catastro- overall disasterâ€? (USGS 2003, 7). phe (table 1.2). The catastrophes in each cate- In the humid tropics, high-intensity and gory are likely to have different return periods, high-duration rainfall events act as the main TAB L E 1.2  Categories of catastrophe CATEGORY DEFINITION 0 Extreme natural event No fatalities, no property damage 1 Small-scale loss event > 1 fatality and/or small-scale damage 2 Moderate loss event > 10 fatalities and/or damage to buildings and property 3 Severe catastrophe > 20 fatalities, overall losses > $50 million 4 Major catastrophe > 100 fatalities, overall losses > $200m 5 Devastating catastrophe > 500 fatalities, overall losses > $500 million 6 Great natural catastrophe Thousands of fatalities, economy severely affected, extreme insured losses Source: © Münchener Rückversicherungs-Gesellschaft, Geo Risks Research, NatCatSERVICE 2011. CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   9 impact of rainfall-triggered landslides in areas F IG U R E 1 . 5  Exposure and fatalities of unauthorized housing is well recognized: associated with rainfall-triggered landslides, by income class Poverty can compel people to migrate to larger cities in search of employment oppor- a. Exposure tunities. Without the economic means to par- number of people per year ticipate and integrate into town and city soci- 1,000,000 no data, 1.3% eties, the poor create shantytowns often on low-income country, 19.5% the outskirts of cities in areas with high haz- 100,000 ard exposure risks. For instance, in the case of 10,000 the major rain-induced landslide in Venezu- 1,000 lower-middle-income country, 62.9% ela in 1999, which affected between 80–100 100 thousand people, most of the thirty thousand disaster deaths can be traced back to an infor- 10 upper-middle-income country, 8.4% mal settlement that was washed away during high-income country, 7.9% 0 the event (OAS 2004, 2). As well as causing major landslide disas- b. Modeled fatalities ters, a single rainfall event can trigger numer- average number of people per year (%) ous small- to medium-size landslides (AGS 100 2000)—a scale not recognized in most inter- low-income country, 41.4% 80 national records of disasters. The frequent occurrence of highly localized disasters 60 anticipates the potential for much larger 40 lower-middle-income country, 40.5% disasters. 20 To address landslide-related losses, and the upper-middle-income country, 10.8% high-income country, 7.8% interaction of development activities with 0 slope stability, this accumulation of risk must low income = per capita GNI < $935 be tackled. The ability to mitigate small events lower middle income = per capita GNI $936–$3,705 effectively, or to limit their impact, could result upper middle income = per capita GNI $3,706–$11,455 high income = per capita GNI > $11,456 in an increased capacity to manage the risks Source: UNISDR 2009. associated with larger events (Bull-Kamanga et al. 2003). Note: GNI = gross national income. Landslide risk and MoSSaiC With respect to rainfall-triggered landslide trigger for landslides by reducing the shear risk, the Caribbean (where MoSSaiC has been strength of the slope materials. Some climate developed) is typical of many developing change predictions suggest an increase in the regions in the humid tropics. The steep slopes number and intensity of extreme rainfall and deep soils that characterize much of this events in these regions. However, even with- region are naturally prone to landslides, which out climate change, the susceptibility of slopes are triggered by high-intensity or high-dura- to landslides is being increased by develop- tion rainfall (Lumb 1975). ment activities involving earthworks (cuts and A combination of poverty and increasing fills) and construction—whether planned or levels of urbanization is resulting in the con- unauthorized. These activities change slope struction of unauthorized settlements on such geometry, strength, loading, vegetation cover, slopes, as they are often the only available and surface water and groundwater regimes. location for the poor (Board on Natural Disas- Thus, the process of development can increase ters 1999). Like many other developing coun- the physical landslide hazard while exposing tries, urban areas in Latin America and the more of the most vulnerable people and struc- Caribbean suffer from low-quality housing, tures to these hazards. The occurrence and inadequate (or unenforced) urban planning 1 0    C H A P T E R 1 .   F O U N DAT I O N S : R E D U C I N G L A N D S L I D E R I S K I N CO M M U N I T I E S FI G U R E 1.6  Global rainfall-triggered landslide fatalities modeled fatalities per million per year (relative) risk class 100 10 Dominica 9 Comoros 8 7 São Tomé and Principe St. Lucia 6 Solomon Islands 10 Vanuatu 5 San Marino Liechtenstein Timor-Leste Cape Verde 4 Fiji Mauritius Monaco New Caledonia Papua New Guinea 3 Montenegro Belize Bhutan Sierra Leone Guatemala Brunei Darussalam Equatorial Guinea 2 Costa Rica Haiti Jamaica Albania El Salvador 1 Trinidad and Tobago Nicaragua Nepal Iceland Panama Lao PDR Lebanon GeorgiaHonduras 1 Liberia Ecuador Malta Guyana Slovenia Guinea Cameroon Ethiopia Malawi Madagascar Myanmar Cyprus Lesotho Armenia Croatia Benin Kenya Philippines Macedonia, FYR Eritrea Bolivia Korea, Dem. People’s Rep. Colombia Gambia Malaysia Namibia Togo Tanzania Indonesia Kyrgyzstan Austria Yemen, Rep. Swaziland Ireland Norway Serbia Côte d’Ivoire Mexico Vietnam Uruguay Korea, Rep. Nigeria Israel Tunisia Afghanistan Italy Turkey Pakistan Oman Bulgaria Iraq Japan 0.1 Czech Republic Niger Argentina Thailand Bangladesh India Moldova Zimbabwe Australia Spain Mali Brazil Slovak Republic Canada Sudan Iran, Islamic Rep. China South Africa France Burkina Faso Hungary United Kingdom Germany Russian Federation Kazakhstan Ukraine Uzbekistan Poland United States 1 10 100 modeled fatalities per year (absolute) Source: UNISDR 2009. Note: Approximately 2.2 million people are exposed to landslides worldwide, but many small landslide events causing deaths are not internationally reported. controls, and insufficient investment in infra- MoSSaiC is specifically targeted to reduce structure (Charveriat 2000). the frequent small- to medium-size rainfall- The resulting landslide risk is the product of complex interactions between the inherent triggered landslides that occur in weath- susceptibility of slopes to landslides (related to ered soils and that are exacerbated by their soils and geology, topography, hydrology, human influences on slope drainage and and vegetation), the influence of human activi- geometry. It is designed for application in ties in affecting these factors at a highly local- the most economically, socially, and physi- ized scale, and the vulnerability of communi- cally vulnerable communities. ties to the impact of landslides. 1.3.2 Disaster risk management structure, or the environment) to that hazard, and the vulnerability of those elements to Defining risk damage by the hazard. Risk is commonly DRM requires an understanding of what is expressed as a function of hazard, exposure, driving the risk. This can be broken down into and vulnerability. three components: the physical hazard, the A natural hazard (such as a landslide, flood, exposure of different elements (such as peo- storm, volcanic eruption, or earthquake) is ple, buildings, public utilities, economic infra- defined in terms of its frequency (annual prob- CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 1 ability or return period), magnitude, and type communities will find economic recovery at a particular location or within a wider harder than richer communities. region. Where the likelihood of a particular • The temporal exposure of different groups. hazard is expressed in relative or qualitative Differing degrees of exposure are associated terms rather than as a probability, it is more with being at home (greater probability at appropriate to refer to an area’s susceptibility night than during the day) versus being in a to the hazard. school or workplace (greater probability The exposure of people, structures, ser- during the day than at night). vices, or the environment to a specific hazard is determined by the spatial and temporal • The temporal vulnerability of a group in location of those elements with respect to that a specific location exposed to the land- hazard. Vulnerability is an expression of the slide hazard. Differing degrees of physical potential of the exposed elements to suffer vulnerability (injury or loss of life) will per- harm or loss. Thus, exposure and vulnerability tain depending on whether someone is out- relate to the consequences or the results of a doors, in a wooden house, or in a concrete natural force, and not to the natural process structure when a landslide occurs. itself (Crozier and Glade 2005). In many cases, • Variation of vulnerability for different exposure is treated as an implicit part of vul- nerability assessment, as described below. elements. A house may have the same vul- Vulnerability is related to the capacity to nerability to a slow or rapid landslide event, anticipate a hazard, cope with it, resist it, and but people living in the house will have a recover from its impact. It is determined by a lower vulnerability to the slower event than mix of physical, environmental, social, eco- to the rapid event, depending on their abil- nomic, political, cultural, and institutional fac- ity to leave the house. tors (Benson and Twigg 2007). Vulnerability These and other factors need to be consid- may be expressed qualitatively or quantita- ered to assess vulnerability to landslides. tively, in terms of direct or indirect damage Because of the wide range of factors involved, and tangible or intangible damage. The dam- it has been noted that “vulnerability assess- age can be physical, environmental, social, or ment is a complex issue, which is regularly not economic and have an impact at a range of considered in an appropriate and thoughtful local and national scales. The degree of direct mannerâ€? (Crozier and Glade 2005, 27). physical or economic damage is often expressed in cost terms or on a scale of 0–1 The disaster risk management process (from no damage to total loss). Indirect and A typical DRM process will include the follow- intangible damage is usually more difficult to ing steps. quantify. The opposite of vulnerability is resil- ience (of people) or reliability (of structures). Step 1: Disaster risk assessment Vulnerability assessment is especially com- plex for landslides since a wide range of effects • Analyze the risk. Identify and measure the have to be considered, such as the following: frequency, magnitude, and type of hazard; and the vulnerability and exposure of the • The location, type, magnitude, and veloc- elements at risk. ity of the landslide hazard­ . These will directly determine its spatial impact and • Understand the risk. Identify the underly- the exposure of elements at risk. ing hazard and vulnerability processes, causes, and effects. • The physical and socioeconomic vulner- ability of groups. Children and the elderly • Evaluate the risk. Compare with other risks or disabled will be able to respond less and decide whether to accept or treat the quickly than others; poorer households and risk. 1 2    C H A P T E R 1 .   F O U N DAT I O N S : R E D U C I N G L A N D S L I D E R I S K I N CO M M U N I T I E S Step 2: Disaster risk reduction impact of potential natural hazard eventsâ€? (Benson and Twigg 2007, 16). Table 1.3 defines • Identify DRR options. some of the terms commonly used to describe —— Avoid the hazard. Reduce exposure by DRM components and gives examples of the enforcing planning controls, emergency activities typically involved. evacuation, or permanent relocation. The ultimate goal of DRM is to reduce disas- ter risk to an acceptable level. Figure 1.7 illus- —— Reduce the hazard, usually through trates how this can be achieved via different some form of engineering measures. DRR options (corresponding to those listed in —— Reduce the vulnerability and/or expo- Step 2 above): reducing the consequences, sure. Increase the reliability of struc- directly reducing the hazard, or redesigning to tures using engineering and building reduce both hazard and consequences. controls; or the resilience of people The concept of acceptable risk through public awareness, early warn- ing, and planning for disaster response Elimination of risk is rarely feasible; however, and recovery. mitigation measures can reduce risk. Risk reduction is thus undertaken in the context of —— Transfer the risk, using disaster funds seeking to achieve what society and the com- and insurance. munity regard as “acceptable riskâ€? (or “tolera- • Plan the risk treatment. Design the selected ble riskâ€?). According to the International risk treatment option. Union of Geological Sciences Working Group on Landslides, acceptable risk can be defined • Implement the risk treatment. as “a risk that society is willing to live with…in • Monitor the risk. the confidence that it is being properly con- trolled, kept under review, and further reduced Taken together, DRR measures are often as and when possibleâ€? (Dai, Lee, and Ngai referred to as mitigation. Mitigation encom- 2002, 78). When considering acceptable risk passes any structural (engineering) or non- criteria for landslides, the following general structural (planning, policy, public awareness) principles, defined by the International Union measures “undertaken to minimise the adverse of Geological Sciences, could be applied: TAB L E 1. 3  Disaster risk management components COMPONENT EXAMPLE ACTIVITY Risk Risk identification, • Hazard mapping, prediction and monitoring assessment analysis and evaluation • Community vulnerability assessment • Social risk perception analysis • Risk mapping Ex ante risk Risk prevention and • Planning controls reduction mitigation • Building codes • Structural hazard reduction measures • Risk financing: risk transfer (insurance), risk retention (funds) Disaster preparedness • Public awareness • Early warning • Institutional strengthening Ex post Disaster response • Emergency management disaster • Humanitarian relief management Disaster recovery • Postdisaster needs assessment • Reconstruction and rehabilitation CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 3 • Tolerable risks may vary from country to F IG U R E 1 .7  Disaster risk management country and within countries, depending options on historic exposure to landslide hazard, and the system of ownership and control of large reduce redesign slopes and natural landslide hazards (Dai, (loss of life, cost, indirect impact) consequences Lee, and Ngai 2002, 78). ar t Defining acceptable risk is complex, and er’s consequences ne only in the most data-rich circumstances can it gi en be seriously attempted in a quantitative man- ner. Figure 1.8 illustrates the definitions devel- oped in Hong Kong SAR, China. Figure 1.8a illustrates a preferred definition, in that there accept reduce hazard is no acceptable risk zone defined; figure 1.8b small illustrates an alternative definition where it is low hazard high (probability of failure) considered reasonable for society to accept a certain level of risk. Source: International Center for Geohazards, Norway. Such numerical formulations, and associ- ated representations, of risk are only a guide to what a given society might accept. More com- monly, social and political judgments are made • The incremental risk from a hazard to an individual should not be significant com- on a case-by-case basis to help determine pared to other risks to which a person is acceptable risk (Bunce, Cruden, and Morgen- exposed in everyday life; stern 1995; Dai, Lee, and Ngai 2002) and guide measures that are actually implemented. • The incremental risk from a hazard should, wherever reasonably practicable, be 1.3.3 Recent influences on disaster risk reduced i.e., the As Low As Reasonably Practicable (ALARP) principle should management policy and implications for apply; MoSSaiC • If the possible loss of life from a landslide Shift from ex post to ex ante policies incident is high, the risk that the incident might actually occur should be low. This The increase in disaster risk described above accounts for the particular intolerance of a has been recognized and responded to by pol- society to incidents that cause many simul- icy makers, governments, and development taneous casualties; agencies. DRM and DRR are now an estab- • Persons in the society will tolerate higher lished part of the extensive development liter- risks than they regard as acceptable when ature, and are increasingly being main- they are unable to control or reduce the risk because of financial or other limitations; streamed in policy—often in conjunction with climate change adaptation and poverty reduc- • Higher risks are likely to be tolerated for tion programs. This recognition has been the existing slopes than for planned projects, product of, and has contributed to, the com- and for workers in industries with hazard- ous slopes, e.g., mines, than for society as a plexity of the DRR advocacy and disaster whole; response landscapes (figures 1.9 and 1.10). Notwithstanding, experts maintain that there • Tolerable risks are higher for naturally occurring landslides than those from engi- is still insufficient global focus on and commit- neered slopes; ment to DRR (Sweikar et al. 2006). As a long- term, low-visibility process that offers no • Once a natural slope has been placed under monitoring or risk mitigation measures guarantee of tangible rewards, disaster mitiga- have been executed, the tolerable risks tion is often overlooked by both sustainable approach those of engineered slopes; development projects and the more immedi- 1 4    C H A P T E R 1 .   F O U N DAT I O N S : R E D U C I N G L A N D S L I D E R I S K I N CO M M U N I T I E S FI G U R E 1.8  Societal landslide risk in Hong Kong SAR, China a. Preferred definition b. Alternative definition frequency per year frequency per year 1.E+00 1.E+00 1.E−02 unacceptable 1.E−02 unacceptable intense intense 1.E−04 scrutiny 1.E−04 scrutiny region region ALARP 1.E−06 ALARP 1.E−06 broadly acceptable 1.E−08 1.E−08 1 10 100 1,000 10,000 1 10 100 1,000 10,000 n or more fatalities n or more fatalities Source: Dai, Lee, and Ngai 2002. Note: ALARP = as low as reasonably practicable. ate concerns of humanitarian aid responses to after the event (Mechler, Linnerooth-Bayer, disasters. Even though it is acknowledged that and Peppiatt 2006). ex ante risk reduction is likely to be preferable The emergence of new policy and funding from both humanitarian and economic per- trends generally occurs over a decadal cycle, spectives (Blaikie et al. 1994), 90 percent of which makes recording and reporting on proj- bilateral and multilateral disaster-related ect impact very important, given the lagged funding is still spent on relief and recovery response between funding and project feed- FI G U R E 1.9  International advocacy landscape for disaster risk reduction COALITION NONGOVERNMENTAL BILATERAL MULTILATERAL ORGANIZATION BOND Group (UK) AusAID (Australia) ECHO IWG/ECB Project Action Aid (UK) BMZ (Germany) DIPECHO GDIN Christian Aid (UK) CIDA (Canada) IASC Steering Committee IAWG (Nairobi) Catholic Relief Services DFID (UK) UNDP ICVA IFRC DMFA (Denmark) UN ISDR InterAction Lutheran World Relief FFO (Germany) UN OCHA ProVention Consortium Mercy Corps (UK/USA) GMZ (Germany) UN Special Envoy Sphere Project Oxfam (UK/USA) MOFA (Japan) VOICE PHREE-WAY NMFA (Norway) Plan International (UK) SIDA (Sweden) INTERNATIONAL FINANCE Practical Action (UK) SDC (Switzerland) RESEARCH Red Cross (UK/USA) USAID (USA) African Development Bank ADPC (Thailand) RiskRED US State Department Asian Development Bank ADRC (Japan) Save the Children (UK/USA) Caribbean Development Bank BHRC (UK) Tearfund (UK) Inter-American Development Bank CRED (Belgium) World Vision (UK/USA) International Monetary Fund ODI (UK) The World Bank Source: Sweikar et al. 2006. Note: Organizations listed in italics play an identifiable role in advocacy; those listed in boldface are involved in coordination. CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 5 F IG U R E 1 .1 0  UN disaster response organizational framework UN General Assembly Coordination of humanitarian, policy development, and Disaster Reduction Programme humanitarian advocacy ISDR UNESD Economic OCHA International Strategy for Central Office for the and Social Disaster Reduction Development Register Coordination of Humanitarian Affairs IATF UN/ISDR UNDESA Inter-Agency Task Force Inter-Agency Secretariat Emergency Economic ERC for Disaster Reduction of the ISDR Telecommunications and Social Emergency and Relief Affairs WGET, IASC-RGT, Coordinator and CDC DESC WCDR IDD Support and CMCS IASC World Conference on Inter-Agency Internal Coordination Civil Military Inter-Agency Standing Disaster Reduction Displacement Division to ECOSDC Coordination Committee Section Early Recovery Cluster UNDAW UN Agencies Advancement of Women Crisis prevention and recovery Disaster management programme UNDP Drylands Development Centre Lead Agency RELIEFWEB UNCRD Shelter and sustainable human settlements Regional UN-Habitat Disaster management programme Development HIC Health Action in Crisis, Division of Humanitarianinfo.org WHO Emergency and Humanitarian Action Farming, livestock, fisheries, and forestry, GLIDEnumber Global Information and Early Warning FAO System, GeoWeb UNDMTP Hunger as a result of natural disasters and World Food Training Virtual OSOCC food security in developing countries Programme Programme Environmental issues in disaster management, Information system DEWA (early warning and assessment), UNEP GRID (information database), APELL ProVention (emergencies at the local level) Consortium Rapid assessment and Health, education, equality, and UNICEF protection of children in disasters international coordination on-site Prevention strategy, global early warning UNESCO IRIN UNDAC system, and impact assessments News United Nations UNHC Assessment and Human rights of displaced people Service Human Rights Coordination Team Search and rescue UN Regional Agencies INSARAG International Search and UNECA CEPAL UNECE UNESCAP UNESCWA Rescue Advisory Group Africa Latin America Europe Asia and the Western and the Caribbean Pacific Asia Source: Lloyd-Jones 2006. back. If something works, evidence needs to be ever, on-the-ground delivery has not material- given, since this is the driver for further policy ized in a correspondingly significant way. change and funding. The shift of emphasis Wamsler (2006, 159) notes: from an ex post (response and recovery) to an During the past three decades policy state- ex ante (mitigation and preparedness) ments by all major agencies have included approach to disasters has been reflected in the risk reduction as a pre-condition and an portfolio of projects funded by development integrated aspect of sustainable develop- banks for a number of years (IDB 2005). How- ment… but when it comes to practical imple- 1 6    C H A P T E R 1 .   F O U N DAT I O N S : R E D U C I N G L A N D S L I D E R I S K I N CO M M U N I T I E S mentation, comparatively little has been hazard, and the community basis for delivery done. on the ground. The following discussion A recent World Bank project evaluation explores recent influences on ex ante DRM study provides clear evidence that disaster policy in relation to these three areas, with preparedness and mitigation need to be particular reference to landslide risk and the addressed as a priority (table 1.4). importance of the government-community Despite the seeming shift to ex ante DRM relationship. This discussion provides the pol- policy, there is an apparent lag in funding and icy context for MoSSaiC. consequently in the delivery of that policy on Need for evidence that mitigation pays the ground. With respect to landslide risk reduction, the following appear to be the key Studies undertaken with respect to specific issues: DRM projects have consistently indicated that mitigation pays (World Bank 2010b): in gen- • Decision makers will not naturally choose eral, for every dollar invested, between two to invest in a project with unseen benefits and four dollars are returned in terms of (the main benefits of DRR are in the future avoided or reduced disaster impacts (Mechler in terms of losses avoided). 2005; Moench, Mechler, and Stapleton 2007). • A top-down policy approach to DRR can, in On the other hand, some cases, actually make it difficult to Building a culture of prevention is not easy, identify local physical risk drivers and however. While the costs of prevention have thereby find a practical solution to the haz- to be paid in the present, its benefits lie in the ard. distant future. Moreover, the benefits are not tangible; they are the wars and disasters that • The top-down approach often fails to do not happen. So we should not be surprised engage with the most vulnerable, who will that preventive policies receive support that therefore not be motivated to adopt new is more often rhetorical than substantive (Annan 1999). practices or own the mitigation measures. Thus, practical implementation of landslide Evidence suggests that an individual’s deci- mitigation measures in vulnerable communi- sion-making process will be biased against the ties is rare, and so is evidence of the effective- activities and costs involved in reducing the ness of mitigation. risk of low-probability, high-consequence Three interrelated areas need strengthen- events. Meyer (2005) argues that our ability to ing—the evidence base for investment in risk make optimal mitigation decisions is hindered reduction, the scientific basis for reducing the by three deep-rooted biases: TAB L E 1.4  Lessons learned from World Bank natural disaster projects MENTIONS IN IEG RANK LESSON LEARNED DATABASE 1 Disaster management, preparedness, and mitigation need to be addressed 49 2 Simple and flexible procurement is fundamental to expeditious implementation 40 3 Lessons regarding project coordination units and/or working with existing agencies (pros and cons) 31 4 Maintenance is critical for sustainability 25 5 Simple project design is more important when activities to be implemented are urgent 25 6 Community participation produces several identifiable benefits 25 Source: IEG 2006. Note: Lessons are from 303 completed World Bank natural disaster projects as identified by the World Bank’s Independent Evaluation Group (IEG). CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 7 • How we learn from the past—We tend to investments to be compared. For example, learn by focusing on short-term feedback. modeling the costs and benefits of preventing hurricane damage to properties (by protecting • How we see the future—We tend to see the windows and doors and upgrading roofs) in future as a simple extension of the present two villages in St. Lucia demonstrated attrac- rather than anticipating low-probability tive benefit-cost ratios for a wide range of events such as disasters. potential discount rates (Hochrainer-Stigler et • How we make the trade-off between imme- al. 2010) (figure 1.11). diate capital investment in risk reduction Cost-benefit analysis uses a discount rate to compared with future savings in avoided compare economic effects occurring at differ- losses—We tend to overly discount the ent times. Discounting converts future eco- value of ambiguous future rewards com- nomic impacts to their present-day value. The pared to short-term costs. discount rate is usually positive because resources invested today can, on average, be Taken together, Meyer argues, these limita- transformed into more resources later. If hur- tions seem to explain many of the biases that ricane mitigation is viewed as an investment, have been observed in real-world DRM deci- the return on that investment can be used to sions—and, most critically, why we seem to decide how much should be spent on mitiga- have such difficulty correcting them. To over- tion. Assuming a 25-year project lifetime and a come these biases, it is even more urgent that 12 percent discount rate, the example in fig- physical evidence be provided for the effective- ure  1.11 shows such an intervention yields a ness of DRR—not just on the basis of economic benefit-cost ratio of 1.5:1—in other words, it investment, but also in terms of the social and pays; but with an assumed project lifetime of indirect benefits to those most at risk. only five years, cost exceeds benefit (benefit- An example showing that mitigation pays is cost ratio of 0.75:1). provided by a series of studies conducted by The application of catastrophe modeling to the Wharton School of the University of Penn- wooden homes in Canaries, St. Lucia, illus- sylvania. These studies used catastrophe risk trates how the effect of climate change on the models to enable cost-benefit assessments to benefits of hurricane mitigation measures can be made of mitigation measures. The four be assessed (Ou-Yang 2010). Figure 1.12 shows basic components of a catastrophe model— the change in benefit-cost ratios for different hazard, inventory, vulnerability, and loss— mitigation measures over different time scales enable risk to be quantified in terms of cost (Wharton School 2008). In the case of a hur- ricane, the four components can be defined as F IGUR E 1.11  Benefit-cost ratio for hurricane-proofing prevention measures for follows: houses in Canaries and Patience, St. Lucia • Hazard, quantified by the frequency, mag- benefit-cost ratio nitude, and path of the hurricane 5 • Inventory, the list (or portfolio) of proper- 4 ties exposed to the predicted hurricane 3 25 years • Vulnerability, the susceptibility to damage 2 10 years of the exposed structures 5 years 1 • Loss, the resulting direct or indirect finan- 1 year 0 cial loss to the property inventory 0 2 4 6 8 10 12 14 discount rate (%) For a given hazard, catastrophe modeling Source: Hochrainer-Stigler et al. 2010. allows the costs and benefits of different DRM 1 8    C H A P T E R 1 .   F O U N DAT I O N S : R E D U C I N G L A N D S L I D E R I S K I N CO M M U N I T I E S FI G U R E 1.12  Mitigation benefit-cost ratio for wood frame building in Canaries, St. Lucia, with and without the effect of climate change a. In the absence of climate change b. Incorporating climate change benefit-cost ratio benefit-cost ratio 5 5 4 4 3 3 2 2 1 1 0 0 0 5 10 15 20 0 5 10 15 20 time (years) time (years) roof mitigation (A) opening mitigation (B) roof and opening mitigation (AB) Source: Ou-Yang 2010. Note: 0 percent discount rate assumed. in the absence and presence of climate change. Caribbean governments. It is designed to As expected, benefit-cost ratios increase with limit the financial impact of catastrophic hurricanes and earthquakes to Caribbean time in both cases, but grow faster in the pres- governments by quickly providing short term ence of climate change. This phenomenon is liquidity when a policy is triggered. It is the more significant for longer time scales. After world’s first and, to date, only regional fund 20 years, the benefit-cost ratio is above 4.5:1 in utilising parametric insurance, giving Carib- the presence of climate change, but slightly bean governments the unique opportunity to below 4:1 in the absence of climate change. purchase earthquake and hurricane catastro- phe coverage with lowest-possible pricing The role of disaster risk insurance (CCRIF 2012). How much to invest in risk reduction and how Consensus in this field suggests that insur- much to invest in insurance is a complex ques- ance by governments is not appropriate for tion. For risk reduction, investments are likely to have a better benefit-cost ratio for relatively frequent events than for infrequent low-prob- F IGUR E 1.13  Efficiency of risk management instruments and ability events. Risk insurance, on the other occurrence probability hand, is seemingly less economically rational for frequent low-loss events that may be cov- 500 year Very extreme losses: Residual risk unprotected as not e ective to reduce or transfer risks ered domestically or where the risk may be reduced (Mechler et al. 2010) (figure 1.13). return period There has been growing interest in poten- 100 year Medium-size to extreme losses: tial insurance vehicles for the relatively more Low to Risk ï¬?nancing extreme disaster risks (Kunreuther 2009). An medium-size more losses: Risk e ective example of one such vehicle is the Caribbean reduction more 10 year Catastrophe Risk Insurance Facility: e ective CCRIF is a risk pooling facility, owned, oper- Source: Mechler et al. 2010. ated and registered in the Caribbean for CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 9 frequently occurring risks; rather, expenditure development protected and adaptation to cli- on risk reduction is relevant in such circum- mate change facilitated. Rather than a cost, this should be seen as an investment in build- stances. Since MoSSaiC seeks to reduce land- ing a more secure, stable, sustainable and slide risk by directly addressing local urban equitable future. Given the urgency posed by landslide hazard drivers, it may play a role in climate change, decisive action needs to be reducing the accumulation of just such fre- taken now (UN 2009, 4; emphasis added). quently occurring events. MoSSaiC could also potentially have attractive benefit-cost ratios In the case of landslide risk, there is a need in reducing the landslide hazard associated to better understand landslide hazard drivers with more extreme rainfall events (Holcombe and provide a scientific basis for landslide risk et al. 2011). management. This means understanding the physical processes affecting slope stability Need for science-based risk assessment (and the effect of human activities on those The move toward investment in ex ante DRR physical processes) and the scale at which carries with it the need to assess and address they operate (the hillside/community scale), the underlying risk drivers—hazard, exposure, so that appropriate hazard reduction mea- and vulnerability (defined in section 1.3.2). sures can be identified and implemented. Rel- Risk assessment provides the basis for effec- evant landslide hazard drivers and assessment tive DRM by answering the following ques- methods are introduced in chapters 2, 3, and 4. tions and identifying what risk management The need for the geoscience disciplines to options will be most effective (Ho, Leroi, and inform an integrated approach to landslide Roberds 2000; Lee and Jones 2004):  risk reduction has been widely voiced: • Hazard identification. What are the likely While all regions experience landslide disas- ters, the harm they cause is most acute in types of hazards? developing countries, where the knowledge • Hazard assessment. What is causing each base required to identify landslide prone hazard, and what is the frequency and mag- areas is often either nonexistent or fragmen- tary (UNU 2006). nitude of that hazard? • Identification of elements at risk. What In order to mitigate landslide hazard effec- tively, new methodologies are required to are the elements exposed to each hazard? develop a better understanding of landslide • Vulnerability assessment. What might be hazard and make rational decisions on the the degree of damage to these elements? allocation of funds for management of land- slide risk… this relies crucially on a better • Risk quantification/estimation. What is understanding and on greater sophistication, the risk associated with each hazard? transparency and rigour in the application of science (Dai, Lee, and Ngai 2002, 65, 82). • Risk evaluation. What is the significance of these estimated risks, and what are the Scientific methods for assessing landslide options for managing them? hazard (location, frequency, magnitude) should be combined with an assessment of the The United Nations (UN) has provided vulnerability of those communities exposed to clear recommendations on the need for effec- the hazard, so that the most at-risk communi- tive risk assessment; these call for the underly- ties are identified. The UN’s specific recom- ing risk drivers to be addressed: mendations are as follows: A failure to address the underlying risk driv- • Shift the emphasis of social protection from ers will result in dramatic increases in disas- an exclusive focus on response to including ter risk and associated poverty outcomes. In pre-disaster mechanisms and more effec- contrast, if addressing these drivers is tive targeting of the most vulnerable given priority, risk can be reduced, human groups; [and] 2 0    C H A P T E R 1 .   F O U N DAT I O N S : R E D U C I N G L A N D S L I D E R I S K I N CO M M U N I T I E S • Promote a culture of planning and imple- The scale of the map is incompatible with the mentation of disaster risk reduction that scale of the physical processes. builds on government-civil society part- Ideally, the most appropriate use of these nerships and cooperation and is supportive of local initiative, in order to dramatically maps would be to enable the identification of reduce the costs of risk reduction, ensure planning control zones—preventing occupa- local acceptance, and build social capital tion or development of the most landslide- (UN 2009, 5; emphasis added). prone areas and thereby avoiding exposure to the hazard altogether. However, in developing Commentaries by Maskrey (1989), Pelling countries, there is often limited capacity for and High (2005), and Twigg (2001) all bear on enforcing planning controls or for removing the community potential in this context. Social people from such areas. funds are perhaps one example of the formal- If exposure of communities to landslide ization of this type of government–civil society hazards cannot be easily reduced, the next partnership, in that such agencies might be question is whether the hazard or its conse- well placed to contribute to MoSSaiC land- quences can be reduced. Unfortunately, wide- slide risk reduction implementation projects. area landslide susceptibility/hazard maps will not yield answers about what is actually caus- Need to complement national risk maps with ing slope instability on a particular hillside or local studies when a landslide might happen. Without such In the context of international and national an understanding, an appropriate mitigation DRM policies, a natural first step is to attempt approach cannot readily be identified. This to carry out a disaster risk assessment at a mismatch of scales may be one factor leading regional or national scale. This often involves to the observation that, despite numerous using geographic information system (GIS) major regional approaches, the uptake of haz- software to generate maps delineating broad ard maps has been minimal (Opadeyi, Ali, and zones of hazard, vulnerability, and risk. The Chin 2005; Zaitchik and van Es 2003). accuracy and spatial resolution of risk maps As noted, wide-area landslide hazard map- are determined by the quality and resolution ping represents the first step in the risk assess- of the underlying layers of data—multiple ment process. Having identified broad zones digital maps of the different variables that of landslide hazard, the next step is to move to affect hazard, exposure, and vulnerability. a more detailed scale—to go on site to identify For example, landslide hazard may be the local hazard drivers. In this way, MoSSaiC expressed qualitatively, and at low spatial involves communities and government teams resolution, as landslide “susceptibilityâ€? combining local knowledge and scientific according to general maps of slope angle, soil expertise to understand the local slope pro- type, and land use. cesses and identify potential landslide mitiga- In the last decade, there have been signifi- tion measures. Complementing existing wide- cant advances in spatially distributed landslide area landslide risk maps with this bottom-up analysis. Glade and Crozier (2005) review cur- approach can enable national DRM policies to rent qualitative and quantitative approaches to be translated into the delivery of effective mit- the analysis of landslides at scales ranging igation measures. from less than 1:10,000 to greater than The role of social funds 1:750,000. However, even at the most detailed spatial scales, GIS-based mapping methods In seeking to assist the most vulnerable com- are not able to identify detailed slope proper- munities, social funds have had a major role in ties and local landslide mechanisms. National many developing countries and have become landslide susceptibility or hazard maps devel- increasingly focused on vulnerability reduc- oped in this way are effectively decoupled tion as part of DRM. Such funds are often from the dominant local landslide processes. assimilated into government as institutions CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    2 1 and, in certain cases, are better integrated with ability drivers of landslide risk (such as pov- related regional funding agencies. The main- erty reduction or risk preparedness projects). streaming of social funds over recent years A flexible blueprint for landslide risk reduction (figure 1.14), combined with their focus on the policy and practice neediest, makes them a potentially important partner in addressing the physical and social MoSSaiC is designed to deliver effective land- drivers of landslide risk. slide risk reduction measures by Social funds can assist in DRM and contrib- • applying appropriate scientific methods (at ute to elements of disaster risk insurance in the correct physical scale) for understand- the following ways (Siri 2006): ing the physical risk drivers and hence • Setting standards of best practice in infra- reducing the landslide hazard; structure construction • doing so within the context of the commu- • Setting an example by not promoting nity, while encouraging a government-com- rebuilding in hazard-prone zones munity partnership for both the delivery of the measures and ongoing management of • Delivering training activities aimed at slope stability; and thereby strengthening technical capacity to miti- gate the potential impact of natural disas- • providing a basis for development of an evi- ters dence base that mitigation can pay— socially and economically, directly and indi- • Broadening their portfolios to include dam- rectly. age mitigation projects for landslides MoSSaiC assesses the specific landslide risk • Promoting microcredit programs faced by vulnerable communities in two • Generating employment to low-income stages: (1) by using basic risk indicators to groups, thereby reducing the vulnerability identify the most at-risk communities (utiliz- of the poor to disasters. ing any available wide-area landslide suscepti- bility or hazard maps and community vulner- While the MoSSaiC approach is essentially ability assessments); and (2) by undertaking focused on addressing the physical landslide detailed slope feature mapping at the commu- hazard drivers in the most vulnerable com- nity scale so as to understand the precise land- munities, it is important to couple such an slide mechanisms. In densely populated vul- approach with any existing local initiatives nerable communities, infiltration of surface aimed at assessing and addressing the vulner- water is often a significant factor in causing F IG U R E 1 .1 4  Evolution of social fund objectives and activities Late 1980s 1990 Late 1990s 2000 Late 2000s Employment/crisis Centrally driven CDD approaches Support for Agencies take on response infrastructure/ decentralization/ added responsibilities social service CDD/microfinance (such as CCT/ development disaster management) Increased integration into country’s poverty Temporary funds reduction efforts and mainstreaming as legitimate institutions of government Source: de Silva and Sum 2008. Note: CCT = conditional cash transfer; CDD = community-driven development. 2 2    C H A P T E R 1 .   F O U N DAT I O N S : R E D U C I N G L A N D S L I D E R I S K I N CO M M U N I T I E S landslides. Treatment of this hazard involves Landslide-triggering rainfall and climate change designing and constructing drains in key loca- tions to capture surface water; this is under- Many developing tropical and subtropical taken by government teams and community regions are subject to rainfall events that trig- contractors. Evidence of the effectiveness of ger landslides on steep slopes. Certain current the hazard reduction measures is evaluated. climate change predictions point to the likeli- The role of the government in addressing both hood of an increase in the intensity of hurri- the physical and social risk drivers, and at the canes and other extreme rainfall events in correct scale (hillside/community level), is those regions, which could be expected to vital. result in an increase in the number and magni- This approach to community-based land- tude of landslides (Mann and Kerry 2006). slide risk reduction is discussed more fully in The links between climate change, devel- section 1.4. Indeed, this book as a whole aims opment, and DRR are strongly emphasized by to provide a flexible blueprint for this form of international development agencies. For landslide risk management. example, the United Nations International Strategy for Disaster Reduction notes that 1.3.4 Landslide risk and other “Disaster risk reduction and climate change development policy issues mitigation and adaptation share common A range of development policy issues and pro- goals. Both fields aim to reduce the vulnerabil- cesses can result in intensified landslide occur- ity of communities and achieve sustainable rence, including climate change, urbanization, developmentâ€? (UNISDR 2012). This bolsters land-use practices (deforestation, cutting of an earlier statement that “the impact of any slopes for housing construction), and inade- increases in weather-related hazards will be quate management of water and sewage sys- highly asymmetric. Poorer countries that con- tems. Two such issues are useful to introduce centrate most existing risk will be dispropor- at this stage because of their connection to the tionately affected by climate changeâ€? predominant landslide risk drivers MoSSaiC (UNISDR 2009, 20). seeks to mitigate. Where possible, predicted changes in the recurrence intervals of landslide-triggering • Some predictions (e.g., UNISDR 2009) rainfall events should be incorporated in land- maintain that climate change may cause an slide hazard assessment. The risk of not doing increase in the intensity of rainfall events in so may leave a significant public liability, either the humid tropics. Knutson et al. (2010, 157) because the private sector will no longer bear additionally comment that “it must be the risk or due to the increased costs of disas- acknowledged that trend detection is ham- ter recovery (UNISDR 2009). In some cases, pered by the substantial limitations in the even relatively simple structural measures availability and quality of globally available could yield both short- and long-term benefits data.â€? Because rainfall is one of the physical to climate change. Because such measures drivers of landslide hazard, it is possible could include landslide mitigation, MoSSaiC is that climate change could increase the fre- consistent with this policy agenda. quency of rainfall-triggered landslides in this region. Urbanization • Urbanization is a major socioeconomic Societal change is more rapid than climate driver with respect to landslide risk. As change. Four important societal drivers pro- noted above, the activity of developing vide a critical context for the accumulation of landslide-prone slopes can increase land- landslide risk: a significant rise in the global slide hazard, while those living on the population (figure 1.15a), accompanied by slopes tend to be the most vulnerable to increased urbanization (figure 1.15b) and poor such disasters. housing (figure 1.15c), which results in the CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    2 3 most vulnerable having the greatest exposure F IG U R E 1 .1 5  Population growth and to landslide risk (figure 1.5). urbanization drivers of landslide risk Slums will grow on marginal urban land a. Global population growth because the speed of economic growth in billions urban centers is not keeping pace with the 9 combined impact of increasing population and rural-to-urban migration. People move to total world population urban centers hoping to capture a place in the 6 new economy. But this urban inflow outruns the capacity of private employment generation developing countries 3 and government capacity to create infrastruc- developed countries ture (Spence 2011). Housing tenure is also relevant in this con- 0 text. The World Bank (2009) reports that for 1750 1800 1850 1900 1950 2000 2050 low-income countries, the predominant hous- ing tenure is unauthorized (defined by Angel b. Urban/rural population shift 2000 as not in compliance with current regu- lations concerning landownership, land-use percent 80 and planning zones, or construction), with rural share of world population small amounts of squatter housing (table 1.5). 65 The following urbanization factors serve to increase landslide risk: 50 • In many locations, the amount of unauthor- 35 ized housing (approximately 60 percent in urban share of world population areas of the Eastern Caribbean, e.g.) exceeds 20 that of authorized housing. Planning and 1950 1970 1990 2010 2030 associated zoning policies can be expected to have a limited impact in such circum- stances. c. Growth in slum population • Unauthorized or informal housing is often billions 1.50 located on already landslide-prone slopes. Latin America and the Caribbean While typical slope zoning requirements 1.25 for a landslide-prone area suggest that no houses should be built on slopes that exceed 1.00 World more developed 14 degrees (Schuster and Highland 2007), regions 0.75 informal housing settlements are invariably Asia North on hill slopes that are considerably steeper. Africa 0.50 • Unauthorized housing may contribute to 0.25 Sub-Saharan Africa slope instability if residents 0 —— cut slopes at steep angles to provide 1990 1995 2001 2005 2010 2015 2020 benched slopes for additional housing; Sources: a—Soubbotina 2004; b—UN 2007; —— redirect storm runoff so flows are con- c—UN-Habitat 2005. centrated onto portions of slopes that Note: In c, figures for 1995 are interpolated using estimates for 1990 and 2001. Figures for 2005 are are not prepared to receive them; projections. Australia, New Zealand, and Japan are included in the more developed regions. —— add water to slopes from septic systems; or 2 4    C H A P T E R 1 .   F O U N DAT I O N S : R E D U C I N G L A N D S L I D E R I S K I N CO M M U N I T I E S TAB L E 1.5  Percentage of owner occupancy, unauthorized housing, and squatter housing by country income group, 1990 LOWER-MIDDLE UPPER-MIDDLE HOUSING TENURE LOW INCOME INCOME INCOME HIGH INCOME Owner occupancy 33 59 57 59 Unauthorized housing 64 27 9 0 Squatter housing 17 16 4 0 Source: World Bank 2009. —— remove trees, shrubs, and other woody slide-risk reduction, in which community vegetation (Olshansky 1996). residents indicate areas of perceived drain- age problems before assessing options for • The numbers of people living in unauthor- reducing land­slide risk by managing surface ized housing areas have grown very rapidly. water. In Caracas, República Bolivariana de Vene- The activities? Managing surface water in all zuela, it has been estimated that about forms (roof water, gray water, and overland 40  percent of the population lives in low- flow of rainfall water), monitoring shallow ground­water conditions, and constructing income districts (barrios) that grow at an low-cost drain systems. All the work is bid annual rate of about 20 percent (Schuster out to contractors in the com­ munity. This and Highland 2007). end-to-end community engagement encour- ages participa­tion in planning, executing, and The trends in increasing unauthorized maintaining surface water manage­ ment on urban development and landslide risk will high-risk slopes. It produces a program owned by the community rather than continue unless effective mitigation measures imposed by the agency or government. are delivered on the ground. An attendant MoSSaiC has lowered landslide risk by offer- issue for governments to consider is the degree ing the community employ­ ment and risk to which they would regard the construction awareness—and has taken a participatory of landslide mitigation measures as legitimiz- approach to rolling out the program to other ing unauthorized communities in such cir- com­ munities. The program shows that cumstances. This is an issue that would need changing community views of hazard mitiga- to be reviewed when any such project is con- tion can enhance community perceptions about climate risks. It also establishes a feed- sidered for implementation. back loop between project inputs and out- puts, with more than 80 percent of funds spent in the communities, allowing commu- 1.4 MOSSAIC nities and governments to establish a clear link between risk perceptions, inputs, and tangible outputs (World Bank 2010a, 327). 1.4.1 Overview In contrast to more top-down approaches, The 2010 World Development Report provides MoSSaiC has been developed at the scale of this overview of MoSSaiC: communities and hillsides, thus accessing A new way of delivering real landslide-risk community information and slope parameters reduction to vulnerable com­ munities was at a process-relevant scale. This approach piloted by MoSSaiC, a program aimed at enables engagement with residents and gov- improving the management of slopes in communi­ ties in the Eastern Caribbean. ernment experts (including engineers, survey- MoSSaiC identifies and implements low- ors, planners, and community development cost, community-based approaches to land- officers) in order to develop a comprehensive CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    2 5 assessment of likely landslide triggers, the level These three foundations—combining of hazard, and potential impact. Typically, the research, policy, and humanitarian interests to dominant instability mechanism in these deliver evidence for undertaking mitigation densely constructed communities is the infil- and for establishing postmitigation out- tration of rainfall and household water into the comes—require a functional holistic structure slope material—and the concentration of such (figure 1.16). The following chapters detail the flows at landslide-prone locations due to various elements within this structure. altered surface water runoff and slope drainage patterns. Landslide hazard mitigation mea- 1.4.2 MoSSaiC: The science basis sures therefore consist of appropriately located A landslide risk assessment with an appropri- drains to intercept and control surface water, ate scientific basis provides the foundation for the capture of roof water, and the connection of designing an intervention and allows those households to the drainage network. advocating the measures to justify their rec- As introduced in section  1.2, MoSSaiC is ommendations. An understanding of the based on three key foundations (table 1.6)—a mechanisms that trigger landslides and the scientific base that, combined with a commu- scale at which they operate is thus essential. nity base, delivers the evidence base for land- The drivers of landslide risk can be summa- slide mitigation. Management and clear com- rized as follows. munication of this approach, within government and in partnership with the com- • Physical drivers. Landslide hazard results munity, can result in behavioral change from a combination of preparatory factors regarding slope stability practices and policies. relating to slope geometry, soil and geology, TAB L E 1.6  The foundations of MoSSaiC FOUNDATION EXPLANATION MoSSaiC Science base Need to understand the • Identifies localized physical causes of landslide hazard at the correct physical physical drivers for landslide scale (this coincides with the community scale and slope management hazard in order to design practices) appropriate mitigation • Addresses physical causes of landslides at this scale measures • Provides scientifically based justification for community selection and mitigation measures Community base Need to understand the • Focuses on the most vulnerable communities human risk drivers (as they • Engages with the community to identify landslide hazard causes and relate to both the physical solutions, often related to drainage hazard and to vulnerability) and balance government • Employs contractors and workers from the community to construct the policy approaches with drainage measures community-based • Recognizes the role of individuals in reducing landslide risk participatory solutions • Builds in-house teams of managers and expert practitioners to work with communities and deliver the mitigation measures • Encourages government-community partnerships Evidence base Need to provide evidence • Delivers appropriate physical works to reduce landslide hazard that landslide mitigation • Delivers the majority of project funding and time in the most vulnerable pays communities • Demonstrates the benefits and cost-effectiveness of community-based landslide risk reduction to decision makers • Changes the local risk perception and encourages behavioral change with respect to sustainable management of slope stability in communities 2 6    C H A P T E R 1 .   F O U N DAT I O N S : R E D U C I N G L A N D S L I D E R I S K I N CO M M U N I T I E S FI G U R E 1.16  MoSSaiC architecture—integrating science, communities, and evidence SCIENCE BASIS Slope mapping of landslide hazard factors: Hazard assessment—qualitative and · local slope geometry and surface drainage quantitative modeling to: angles, heights, lengths, convergence · define the hazard · soils and geology landslide likelihood or probability strata, depth, strength, and drainage properties (frequency), location (magnitude) · surface cover and loading · understand the hazard vegetation, structural loading, point water sources landslide hazard causes and solutions Slope mapping of exposure and vulnerability factors: Vulnerability assessment: · elements exposed to potential landslides · describing the vulnerability house locations, number of persons, house construction n elements affected, potential damage Community: · vulnerability of elements (different measures) · understanding the vulnerability leaders, damage potential (0–1), socioeconomic vulnerability local construction practices, vulnerability organizations, · cost of a landslide drivers residents, direct loss ($), indirect loss ($), intangible loss contractors Government: Landslide risk assessment management, Determine landslide risk as a function of hazard, exposure and vulnerability for each experts, community technicians, practitioners Landslide risk management Prioritize communities, design hazard reduction interventions, calculate costs and benefits of different options Implement hazard reduction measures: Audit outputs and outcomes: · community engagement · technical/physical effectiveness consensus, awareness, communication observed hazard reduction, construction quality · construction · cost-effectiveness local contractors, materials, training, project efficiency, benefit-cost ratio supervision · behavioral change increased awareness, capacity, good practice COMMUNITY BASIS EVIDENCE BASIS vegetation, surface water and groundwater infrastructure, changing the vegetation, regimes, and triggering mechanisms such as and consequential changes in slope surface rainfall and seismic events. Tropical regions water and groundwater regimes. The pres- are especially susceptible to landslides sure of development and population growth because of high-intensity and -duration on available land means that the poorer, rainfall in the context of the deep soils (often most vulnerable sections of society are liv- on steep slopes) in such environments. ing on the most-marginal, landslide-prone hillsides (figure 1.17). • Anthropogenic contributors. Even with- out climate change, anthropogenic activi- MoSSaiC is designed to address a very sig- ties are increasing landslide risk in some of the most vulnerable urban communities in nificant subset of landslide types: rotational developing countries. These activities and translational slides in predominately include altering slope geometry with earth- fine materials (soil) that are principally trig- works (cut and fill at the scale of household gered by rainfall. plots), loading slopes with buildings and CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    2 7 historical and biophysical dataâ€? (Zaitchik and F IG U R E 1 .1 7  Housing stock can reflect van Es 2003, 267). community vulnerability One reason for the lack of application of wide-area landslide maps is that they fail to capture many of the physical landslide hazard drivers that occur at a more detailed scale, and so cannot be used to develop physical land- slide hazard reduction measures. Highly local- ized slope features and processes, such as vari- ations in soil type and depth, and soil water convergence, can be critical landslide prepara- tory factors or triggers. These physical pro- cesses operate at scales that are many orders of magnitude smaller than those at which wide- area hazard maps can be resolved. Indeed, maps of soil depths are usually not even avail- able. Some of these parameters need to be resolved at the household scale (1–50  m2). Since identification of landslide mitigation measures can only come from knowledge of a. Because properties such as this can essen- tially be built in a weekend, effective urbaniza- local slope processes pertaining to the poten- tion of slopes can be very rapid. tial landslide trigger, MoSSaiC is designed to look within communities to examine and model the specific human and physical pro- cesses driving the landslide hazard. Landslide risk reduction measures must have a scientific basis The first stage in developing the scientific foundation for landslide risk reduction in communities is to acknowledge the highly localized scale of the physical and human haz- b. Property abandonment can further ard drivers. MoSSaiC therefore takes landslide complicate the issue of land and property titles hazard mapping into the communities. Chap- in vulnerable communities. ter 5 provides guidance on how to do this. The objective of community-based mapping is to observe and scientifically interpret slope fea- tures and processes, and to consider how they Understanding the risk drivers at the local scale vary over both time and space. This analysis Conventional top-down risk reduction initia- should be done at a scale that is capable of tives typically focus on wide-area (100– revealing the precise mechanisms determin- 1,000  m2) mapping techniques which can be ing the stability of the slope; this will enable used to identify zones of landslide susceptibil- identification of the potential mechanisms by ity based on the overlay and indexing of topo- which slope stability can be improved. graphic, soil/geology, and vegetation maps. In densely populated unauthorized hous- However, “management-oriented hazard ing communities, it is essential to identify the models have been applied in the developing effects of highly localized surface water world only rarely and with mixed success…in regimes, built structures, and cut slopes. Slope large part because of the limitations of relevant hydrology is one such landslide hazard driver 2 8    C H A P T E R 1 .   F O U N DAT I O N S : R E D U C I N G L A N D S L I D E R I S K I N CO M M U N I T I E S with a high spatial and temporal variability. ery time, benefit-cost ratios, scientific basis, The surface and groundwater regimes in such and sustainable policy uptake. The approach locations will vary over short time scales in goes a long way to reconciling the scale issues response to rainfall events and the addition of and risk drivers (discussed above) encoun- household water to the slope. Slope instability tered in delivering effective landslide risk is often increased where metered water is sup- reduction. plied to households in the absence of any sur- The aim of MoSSaiC is to engage with the face water drainage. In the Caribbean, where community, recognize its vital role in under- housing density can approach 70 percent of standing and managing slope stability, and the slope surface cover, the effect is to nearly build its capacity to do so. Simultaneously, the double the amount of surface water going onto community becomes the classroom for the the slope compared with that of annual rain- government teams to exercise their own fall (Anderson and Holcombe 2006). expertise, develop partnerships with the com- MoSSaiC employs a different approach to munity, and establish good technical and man- that used in generating wide-area hazard agerial practices with respect to landslide risk. maps. Landslide hazard mapping is carried All too often, “aid flows from those who out at a much more detailed scale (1:500 or happen to be strong, to those who happen to more) so that specific locations of landslide be weak, reflecting an inherently unbalanced hazard can be identified and the physical driv- power relationshipâ€? (Curtis 2004, 422). An ers understood. This understanding of physi- example of such an imbalance was identified cal landslide drivers underpins design and by Green, Miles, and Svekla (2009) in an analy- implementation of appropriate hazard reduc- sis of the institutions involved in DRR in the tion measures. most vulnerable settlements in Guatemala So, while large-scale landslide hazard maps City. The relationship among the stakeholders, generated as a result of top-down government shown in figure 1.18, suggests that policies may provide an indication of approxi- [T]here are minimal opportunities provided mate landslide zones, MoSSaiC practitioners by external actors to precarious settlement must work at the highly resolved spatial scales residents to influence the allocation of funds coincident with the dominant slope process used in improving the settlements…quite lit- controls. This requires observation and inter- erally, money flows around the precarious settlements, but not directly into them pretation of slope processes on the ground, (Green, Miles, and Svekla 2009, 53). with the support of appropriate scientific tools, in order to provide a scientific basis for Such imbalances are within a context of delivering landslide risk reduction measures potential network instability, with a small in communities. change in that context (e.g., political turnover) potentially causing the network to collapse. The MoSSaiC methodology is intended to MoSSaiC aims to redress such imbalances reduce existing landslide risk and not to affecting vulnerable communities by affirming and strengthening the community focus for encourage, and provide for, the construc- risk reduction. For MoSSaiC, “community tion of houses on slopes deemed landslide basedâ€? means engaging and working with prone. communities to jointly find and deliver solu- tions to landslide risk. 1.4.3 MoSSaiC: The community basis Learning from communities Residents influence the key variables underly- With top-down advocacy and managerial sup- ing the complex system of landslide risk and port, local-scale landslide risk reduction can disaster occurrence. A San Salvador slum have tangible benefits in terms of project deliv- dweller acknowledged the constant efforts CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    2 9 FI G U R E 1.18  Stakeholder connections in Guatemala City’s precarious settlements, showing how money flows around, but not into, the settlements Settlement risk assessment Settlement advocacy/lobbying Nongovernment Donors Informal Private NGOs sector sector Labor Settlement advocacy/ Labor Materials Development lobbying regulations, Infrastructure Services, taxes repair, Infrastructure, infrastructure revegetation, materials, Residents emergency information planning Legal Settlements Infrastructure, neighborhoods Access legalization, and downstream capacity building, issues Lobbying food for legalization Development CIV regulations, (Ministry of Communications, taxes Infrastructure and Housing) Services, Settlement infrastructure Votes risk Votes assessment Government Development CONRED Central SEGEPLAN regulations (National Coordinating Agency (Presidential Secretariat for Municipalities for Disaster Reduction) government Planning and Programming) Special project Special project requests rankings money Development banks, oversight international Ministry of Finance services assistance, taxes Source: Green, Miles, and Svekla 2009. individuals make in coping with disasters and (and increasing) risks such as landslides, disaster risk: “We are always trying to improve, understanding the concerns of the residents is little by little, step by step, in order to become critical. In this respect, identification of the more secureâ€? (Wamsler 2007, 118). landslide hazard and appropriate landslide Household strategies to reduce risk are risk reduction measures properly begins with diverse and include physical/technological, learning from communities (figure 1.19). environmental, economic, social/cultural, This learning process must extend to organizational, and institutional measures understanding the way in which the commu- (table 1.7). nity functions and how MoSSaiC can best be Because such DRR activity may be taking applied in that context. The guidance and place in a vulnerable community at the house- methods presented in this book should serve hold level, it is important to establish the as a flexible blueprint toward this end. degree of this activity and build on it through Identifying the most sensitive and effective MoSSaiC. As Rayner and Malone (1997, 332) means for engaging with each community will note, “adaptation is a bottom-up strategy that also provide the best opportunity for residents starts with changes and pressures experienced to “ownâ€? the project and adopt good slope in people’s daily lives.â€? Whether a community management practices for themselves (fig- is adapting to climate change or to existing ure 1.20): 3 0    C H A P T E R 1 .   F O U N DAT I O N S : R E D U C I N G L A N D S L I D E R I S K I N CO M M U N I T I E S TAB L E 1.7  Coping mechanisms deployed by individual residents in vulnerable communities to reduce landslide risk FOCUS/AIM ACTIVITY IDENTIFIED • Increasing inclination of roofs (for better runoff without damaging roof constructions) • Prolonging roof projections/eaves (to protect houses and pathways from damage/erosion) • Changing direction of roof inclination (so rainwater is discharged without causing damage/landslides) • Installing provisional gutters as roof eaves (so rainwater is discharged without causing damage/landslides) • Replacing mud walls with brick walls, wooden pillars with metallic ones, and corrugated iron with more Constructive durable materials (to better withstand earthquakes, rain, and/or floodwater) structural house • Regularly replacing corrugated iron, wooden pillars, and beams (to better withstand rain or earthquakes) improvements • Improving roof fittings (to better withstand earthquakes and windstorms) • Regularly covering walls and floors with (additional) cement (for better runoff without causing damage/erosion) • Filling cracks with cement (for better runoff without causing damage/erosion) • Closing holes in corrugated iron sheets using special fillings or patches on top of or under sheets (to prevent water entering the house) • Changing the locations of latrines and wash places (to mitigate landslides) • Blocking wastewater pipes with stones and other objects when river levels rise (to avoid flooding and/or related contamination) Nonconstructive • Putting wood or bricks on the roof (to hold it in place during high winds) nonstructural • Putting plastic sheets on the roof, on the inside walls, or over the bed (to prevent water entering or house damaging the house) improvements • Building water barriers in front of the house (to prevent water entering the house) • Digging water channels in earth floors inside the house (for better runoff without causing damage/erosion) • Putting pots under roofs with holes (to catch water, preventing damage/erosion) • Strengthening pathways by covering them with (additional) cement and filling cracks (to mitigate landslides and minimize damage caused by rain and earthquakes) • Filling in former latrine holes with earth, stones, and/or cement (to mitigate landslides and minimize damage caused by rain and earthquakes) Constructive • Repairing public infrastructure that passes through the settlement, such as wastewater pipes (to avoid structural flooding and related contamination) improvement of • Building provisional water channels with corrugated iron or cement (to discharge rainwater without causing the surrounding damage/landslides) living • Building fences to hold back soil (mitigating landslides) and/or to prevent children from falling (fences are environment made of corrugated iron, mattress springs, wooden pillars, and wire netting) • Compacting soil (to mitigate landslides and minimize damage caused by rain and earthquakes) • Building retaining walls or embankments from old tires, stones, and cement; old tires and soil; bricks and cement; stones only; nylon bags filled with soil and cement; and other materials (to mitigate landslides and minimize damage caused by earthquakes) • Putting plastic sheets on slopes, often during entire year (to mitigate landslides) Nonconstructive nonstructural • Digging water channels in earth outside the house (to discharge rainwater without causing damage/landslides) improvement of • Avoiding obvious flood- or landslide-prone locations for house expansion the surrounding • Replacing eroded earth with new earth (to mitigate landslides and minimize damage caused by rain and living earthquakes) environment • Cleaning water gutters (to mitigate flooding) Use of natural • Planting vegetation to prevent landslides resources to reduce risk Removal of • Cutting down bigger branches and trees located close to houses (to minimize the risk of them falling down natural resources and causing damage during earthquakes and landslides) representing risk Cleanup of • Cleaning waste from slopes (to mitigate flooding caused by blocked water gutters) natural • Replacing eroded earth with new earth (to mitigate landslides and minimize damage caused by rain and environment earthquakes) Source: Wamsler 2007. CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    3 1 causality of landslide risk, which is intrinsi- F IG U R E 1 .1 9  Learning from community cally linked to the activity of individual house- residents holds in terms of water and slope management practices. There is no blanket solution, as top- down hazard mapping approaches so often implicitly suggest. For this reason, the knowl- edge of all community members is vital in gaining an understanding of the highly local- ized slope processes leading to landslides. Working toward community-owned solutions A critical component of the MoSSaiC method- ology is to discuss with residents why land- It is important to spend time in communities talking with residents and learning from them slide risk drivers can vary over short distances, about their perceptions of risk and of any and therefore why they should expect that dif- landslide occurrences within the community, ferent hazard reduction measures may be however minor. needed on different parts of the hillside. Understandably, householders are anxious that they will tangibly benefit from such mea- F IG U R E 1 . 2 0  Effects of prompt and sures and will need reassurance, for instance, informed action that a drain built upslope of their house will actually help them even if it is not on their property. That such a decision (the design of the community drainage system) is not an imposed solution, but one that the community has taken ownership of from the beginning is important—not least for residents in vulnera- ble communities who are too often the sub- jects of development rather than active par- ticipants in the process. Numerous methods exist for community Prompt drainage action by the owner, taken participation, but they need to be adapted to while a major landslide rose halfway up the the local context; nearly all require facilitation house’s rear wall, undoubtedly saved this and other forms of support from the govern- property from being lost. The resident had reported earlier minor slides in the same ment or from nongovernmental organizations location. (NGOs). Transparency and effective commu- nication are essential to maintaining engage- ment and credibility with and within the com- A community-based approach aims to reduce their socially constructed vulnerability by munity during the reconstruction process. involving communities as active participants Engaging the community in a disaster program. There is also a broaden- ing consensus that it is cost-effective to train A good risk reduction strategy engages com- and educate communities about risks they munities and helps people work together to face, provide them access to resources and minimize risk. Participation should be by the knowledge, and to develop community-based preparedness and mitigation programs (World entire community, particularly women, young Bank 2007). people, and all livelihood groups—a point that should be clearly communicated to the com- Such considerations are important in munity. Community engagement is valuable understanding the precise physical and social for the reasons given in table 1.8. 32    C H A P T E R 1 .   F O U N DAT I O N S : R E D U C I N G L A N D S L I D E R I S K I N CO M M U N I T I E S TAB L E 1.8  Value of community engagement VALUE EXPLANATION Allows community Community-based approaches require a somewhat different programming knowledge and scientific flow that begins with mobilizing social groups and communities and having understanding of hazard them fully involved in the risk assessment process and vulnerabilities to be combined Reveals community “The communityâ€? is not a monolith, but a complex organism with many subgroups alliances and subgroups; it needs to be engaged in order to identify concerns, goals, and abilities, but there may not be consensus on these items Provides high-resolution The scale at which community engagement is most effective may be quite information small—for example, as few as 10 families; individuals may contribute valuable information on landslide processes at the scale of 1–50 m2 Can reveal different Engagement of the community may bring out different preferences and perceptions to those of expectations, so agencies involved must be open to altering their precon- government ceived vision of the landslide risk management process Builds skills within the Strengthens community skills and capacity for assessing landslide risk, community constructing drainage measures, maintaining the intervention, and developing sustainable slope management practices; training can play an important role in building a community’s capacity to take on project responsibilities Delivers social outcomes Empowers individuals, increases local capacity, strengthens democratic processes, and gives voice to marginalized groups Assists program Creates a sense of ownership, improves program quality, mobilizes resources, effectiveness and stimulates community involvement in execution Source: World Bank 2010c. Participation empowers communities; how- • infuse political issues at the national level ever, the outcomes of that participation can be into the proposed community project. unpredictable. The participatory process may Other behaviors possibly arising during dis- • give rise to new actors and stakeholders; cussions with community residents are that • create conflicts among organizations that community members may not be immediately had previously worked together harmoni- forthcoming with their perspectives, may ously; downplay the significance of threats, or may reserve judgment until they see something • give a platform to vocal individuals whose tangible (UNDP 2008). views are not shared by the majority; Communities participate in MoSSaiC proj- • inflame preexisting, but hitherto dormant, ects through five activities: tensions within the community; • Provision of information on slope features • raise expectations beyond delivery possi- and landslide hazard bilities, insofar as community perceptions • Organization of community meetings and may differ from information residents are coordination with government teams actually given; • Involvement in identifying the landslide • engender “mirror politics,â€? with commu- hazard reduction measures nities potentially feigning agreement in order to divert opportunities to other ends; • Construction (possibly also including con- and tracting and procurement) CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   33 • Monitoring and maintenance of landslide bilities, and new ideas for activities and mitigation measures projects emerge. Trained facilitators and other experts in community participation should be Building government capacity part of the MCU to ensure such synergies. Governments often have sufficient technical and managerial skills that can be harnessed to 1.4.4 MoSSaiC: The evidence base design and deliver landslide risk reduction Decision makers need an evidence base in measures in communities. By creating a cross- order to endorse expenditure on landslide risk disciplinary management unit from such a skill reduction and adopt a proactive ex ante policy base, it is possible to embed MoSSaiC in gov- approach. A typical MoSSaiC project that ernment practice and policy. Chapter 2 is tackles the root causes of landslide hazard will focused on how such a management team— have measurable short-term outputs and lon- here referred to as the MoSSaiC core unit ger-term outcomes (table 1.9). (MCU)—can be built. It identifies the types of Types of evidence in-house expert practitioners needed for implementing the various tasks. The methods This book emphasizes the need to identify and tools provided in this book can be adapted evidence of longer-term benefits of landslide to suit the government’s structures, protocols, risk reduction in communities—the actual and practices. The aim is that governments reduction in the hazard, and the direct and adapt and adopt MoSSaiC in a way that can be indirect benefits (financial and social). The sustained and embedded in local practice and delivery of physical landslide risk reduction policy. measures provides the opportunity to observe the benefits in terms of potentially avoided Clear communication in government- landslide occurrence and losses. This form of community partnerships evidence is counterfactual and often anecdotal, Organizing and facilitating community partic- since it is not know what would have happened ipation should not be done on an ad hoc basis. if the physical measures had not been in place. “Unless risk analysis and communication are However, it is still a powerful means of adequately factored in, major differences in demonstrating the benefits of the intervention. perceptions of risk can impede successful pol- Slope stability modeling can provide a means icy design and implementationâ€? (World Bank for quantifying the reduction in the frequency 2010a, 325). It is important to guide the par- or magnitude of landslides. These model ticipation process and make sure that people’s predictions can then be related to the value of expectations are realistic, especially if they the losses avoided (a project benefit) and believe that large amounts of funding are avail- compared with project costs. Less-tangible able. Community-based projects require social benefits and changes in slope thoughtful engagement on the part of the gov- management practice should also be captured. ernment: Chapter 9 presents some potential methods Information, education, and awareness-rais- for developing this evidence base and ing as carried out so far, are at best not enough identifying the extent of behavioral change. to spur people into action and at worst coun- MoSSaiC project outcomes from sample ter-productive… This calls for a different interventions completed in St. Lucia and Dom- approach, where the individual is considered inica are outlined in table 1.10. not merely the passive receiver of informa- tion but an agent in both causes and solutions 1.4.5 MoSSaiC project components (World Bank 2010a, 327). There are nine principle MoSSaiC project When a government-community partner- components, as reflected in the chapters in ship is well configured, there can be a multi- this book. While seven are sequential plier effect as the community realizes its capa- (figure  1.21), two (encouraging behavioral 3 4    C H A P T E R 1 .   F O U N DAT I O N S : R E D U C I N G L A N D S L I D E R I S K I N CO M M U N I T I E S TAB L E 1.9  Basic MoSSaiC outputs and outcomes providing evidence for ex ante landslide mitigation BASIC OUTPUTS AND OUTCOMES MEASURE (EVIDENCE BASE) Quantities Quantity of physical measures constructed, funds disbursed, persons employed, etc. Direct physical benefits: landslide hazard Observation and local knowledge relating to the effect of heavy reduced rainfall events post-intervention (qualitative) Project Modeled/predicted stability of slope for before and after outputs scenarios (quantitative) Additional physical and social benefits to com- Observation and local knowledge relating to the effect of heavy munity: reduced localized flooding, less mud rainfall events post-intervention (qualitative) on paths, improved water supply through Cost-benefit analysis of project rainwater harvesting, improved environment Evidence of behavioral change Institutional uptake of ex ante approach to managing slope stability in communities based on scientific understanding, Longer-term community focus, and evidence of effectiveness project outcomes Community uptake of good slope management practices based on understanding of local slope processes and demonstration of tangible benefits change and project evaluation) are crosscutting These provide the framework for each chapter components relevant from the start of any and are outlined in table 1.11. proposed MoSSaiC intervention and continuing through to the postproject period. 1.4.6 MoSSaiC pilots The nine components can be subdivided MoSSaiC was initially developed and applied into a series of steps that deliver MoSSaiC. in the Eastern Caribbean (table 1.12). Fig- TAB L E 1.10  Broad impacts of community-based landslide risk reduction program in St. Lucia and Dominica, 2005–10 CATEGORY INDICATOR IMPACT (IN 11 COMMUNITIES) Hazard reduction Pre-MoSSaiC: Minor and major failures during low-recurrence-interval events (~1 in 3–5 Physical year 24 hour) with loss of houses in some communities Post-MoSSaiC: No reported failures from Hurricane Tomas (~1 in 500-year 24-hour rainfall event) Project expenditure ~80% of funds spent on materials and community labor profile Intervention cost equates with approximately 2.3% of community relocation costs should a major landslide occur Economic Average cost per community resident ~$250 ~1,000 person-weeks employment for community members Benefit-cost ratio >2.7:1 in a selected community Persons involved Number of households ~750, number of residents ~4,000 Community construc- Residents share with government in terms of design, construction, and, in some cases, tion partnerships cost Community Water supply continuity 450-gallon water tanks supplied to most-deserving residents in selected communities Certification of key A MoSSaiC certification system, resulting in award to three members from different community members communities for their commitment, leadership, and understanding of the MoSSaiC vision Public Media recognition St. Lucia, Dominica, St. Vincent and the Grenadines: TV/radio interviews, news coverage awareness St. Lucia TV 30-minute MoSSaiC documentary commissioned by government Source: Anderson et al. 2010. CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    3 5 F IG U R E 1 . 2 1  MoSSaiC components 1 Foundations: reducing landslide risk in communities 2 Project inception: teams and steps 3 Understanding landslide hazard 4 Selecting communities 8 Encouraging 9 Project behavioral evaluation 5 Community-based mapping for landslide change hazard assessment 6 Design and good practice for slope drainage 7 Implementing the planned works ure 1.22 provides an indication of typical vul- the World Bank (2010b) has assessed the impact nerable urban communities and landslide risk of disasters on GDP over a 40-year period. For drivers in this region. many countries, this impact exceeds 1 percent of Many of the countries in the region are par- GDP; notably, many SIDS fall into this category. ticularly vulnerable to natural disasters The vulnerability of this region is con- (figure  1.23). To enable country comparisons, firmed by the United Nations: TAB L E 1.11  MoSSaiC framework CHAPTER COVERAGE OUTPUT 1. Understand the disaster risk context with respect to landslides Relevance of MoSSaiC 1. Foundations: 2. Understand the innovative features and foundations of MoSSaiC approach to local Reducing landslide risk context Landslide 3. Identify general in-house expertise and the appropriate institutional structures for identified Risk in codifying a local approach toward landslide risk reduction Communities 4. Brief key individuals on MoSSaiC (politicians, relevant ministries, in-house experts) Core unit of team members identified 1. Establish the MCU; define and agree on key responsibilities MCU formed • Identify available experts in government • Form the MCU and establish communication lines with government 2. Identify and establish government task teams; define and agree on key responsibilities Government task • MCU to identify individuals from relevant ministries to form government task teams formed teams (mapping, community liaison, engineering, technical support, communica- 2. Project tions, advocacy) Inception: • Define roles and responsibilities of the teams Teams and Steps 3. Identify and establish community task teams; define and agree on key responsibilities Community task teams • MCU to identify individuals from selected communities to form community task formed teams (residents, representatives, construction teams) • Define roles and responsibilities of the teams 4. Agree on a general template for project steps Project steps deter- • Review project step template and amend as necessary mined and responsibili- ties assigned • Assign team responsibilities to relevant project steps; confirm project milestones (continued) 3 6    C H A P T E R 1 .   F O U N DAT I O N S : R E D U C I N G L A N D S L I D E R I S K I N CO M M U N I T I E S TAB L E 1.11  MoSSaiC framework (continued) CHAPTER COVERAGE OUTPUT 1. Gain familiarity of different landslide types and how to identify those which may MCU and task teams be addressed by MoSSaiC understand the types of • Review landslide process introductory material in this book and other sources landslide risk for which MoSSaiC is applicable 2. Gain familiarity with slope processes and slope stability variables MCU and task teams 3. Understand- • Review landslide process variables as introduced in this book can identify different ing Landslide levels of landslide Hazard hazard and underlying physical causes 3. Gain familiarity with methods for analyzing slope stability MCU and task teams • Review slope stability software as introduced in this book and other sources can provide scientific rationale for landslide mitigation measures 1. Define the community selection process Agreed-upon selection • Identify available experts in government method and criteria, roles and responsibili- • Determine availability of software and data ties, timeline • Request permission to use data if necessary • Design appropriate method for selecting communities 2. Assess landslide hazard List or map of relative • Data acquisition: topography, soils, geology, land use, past landslides landslide susceptibility of different areas • Data analysis: landslide susceptibility or hazard within the study area 3. Assess exposure and vulnerability List or map of relative • Data acquisition: community locations, building footprints, housing/population vulnerability of density, census data or poverty data exposed communities • Data analysis: vulnerability of exposed communities to landslide impacts in 4. Selecting terms of physical damage, poverty, or other criteria Communities 4. Assess landslide risk List or map plus list of • Data analysis: landslide susceptibility/hazard, exposure, and vulnerability data most-at-risk communi- combined to determine overall landslide risk for study area ties for possible risk reduction measures • Data analysis: identify communities exposed to highest levels of landslide risk 5. Select communities Prioritized community • Conduct brief site visits of short-listed communities to confirm results short list • Consult community liaison task team and other relevant local stakeholders to review list • Confirm prioritized community short list according to selection criteria 6. Prepare site map information for selected communities Hard-copy map and • Data acquisition: most detailed maps and aerial photos of selected communities aerial photo for use on site • Map preparation: assemble community maps/photos and print hard copies 1. Identify the best form of community participation and mobilization MCU agrees on 5. Community- • Review and determine the most suitable form of community participation appropriate community Based participation strategy • Identify available community liaison experts in government Mapping for Landslide 2. Include key community members in the project team Key community Hazard • Identify existing or new community representatives members included Assessment • Hold initial discussions with community representatives to brief them on mapping and project rationale (continued) CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   37 TAB L E 1.11  MoSSaiC framework (continued) CHAPTER COVERAGE OUTPUT 3. Plan and hold a community meeting First community • Take advice from government and community representatives on location and meeting held style of meeting • Compile a community base map from existing maps, plans, and aerial photos (see section 4.7) to bring to the meeting 4. Conduct the community-based mapping exercise; this will entail a considerable Community slope amount of time in the community feature map • Talk with residents in each house to begin the process of engagement, knowledge sharing, and project ownership • Observe and discuss wide-scale and localized slope features and landslide hazard • Add local knowledge and slope feature information to the base map 5. Community- Based 5. Qualitatively assess the landslide hazard and potential causes Slope process zone Mapping for • Use the community slope feature map to identify zones with different slope map (relative landslide Landslide processes and landslide hazard hazard) Hazard • Evaluate the role of surface water infiltration in contributing to the landslide hazard Assessment 6. Quantitatively assess the landslide hazard and the effectiveness of surface water Determination of management to reduce the hazard viability of MoSSaiC • Use physically based software or simpler means to assess the likely contribution of approach surface water to landslide hazard • Assess whether reducing surface water is likely to reduce landslide hazard 7. Identify possible locations for drains Initial drainage plan and • For each slope process zone, determine the most appropriate surface water prioritization matrix management approach • Prioritize the zones according to relative landslide hazard 8. Sign off on the initial drainage plan: organize a combined MCU-community Initial drainage plan walk-through and meeting to agree on the initial drainage plan sign-off 1. Identify the location and alignment of drains Proposed drainage plan • Use the slope process zone map and initial drainage plan as a starting point; apply (drain alignments and drainage alignment principles to identify potential drain network alignment dimensions) • Refine alignment details on site 2. Estimate drain discharge and dimensions • Calculate surface water runoff and household water discharge into proposed drains • Calculate required drain size 3. Specify drain construction and design details Full drain specification 6. Design and 4. Incorporate houses into the drainage plan List of quantities Good Practice • Identify houses to receive roof guttering, gray water pipes, water tanks, and needed for household for Slope hurricane straps connections Drainage • Determine how household water will be directed to the drains (via pipes con- nected by concrete chambers or small drains) 5. Produce final drainage plan Final drainage plan and • Include all drain alignment and household connection details on the plan cost estimate • Estimate total project cost from unit costs 6. Stakeholder agreement on plan Sign-off on the final • Meet with the community and refine the plan drainage plan • Complete checks regarding relevant safeguards • Submit plan for formal approval (continued) 3 8    C H A P T E R 1 .   F O U N DAT I O N S : R E D U C I N G L A N D S L I D E R I S K I N CO M M U N I T I E S TAB L E 1.11  MoSSaiC framework (continued) CHAPTER COVERAGE OUTPUT 1. Prepare work package and request for tender documentation Work packages for • Prepare a bill of quantities for the planned works implementation of drainage intervention • Incorporate appropriate contingency and any double-handling costs (i.e., where to reduce landslide material has to be delivered to sites where access is difficult and requires the hazard establishment of a storage site between delivery and construction site locations) • Decide on work package size that maximizes community engagement and meets procurement requirements • Prepare design drawings and plans to accompany each work package • Identify an appropriate plan for procuring materials depending on the community contracting approach, community capacity, and project procurement requirements 2. Conduct the agreed-upon community contracting tendering process Briefing meeting for • Identify potential contractors from the community and provide briefing on proposed contractors held; works and work packages, emphasizing the need for good construction practice community contracts 7. Implement- awarded ing the • Invite tenders from contractors, providing assistance or training on how to submit Planned a tender document Works • Evaluate tenders, award contracts, and brief contractors on safeguards 3. Implement construction Briefing meeting for • Select experienced site supervisors community held; construction under • Authorize start of construction and meet with the community to discuss the way construction process and introduce site supervisors • Closely supervise the works to ensure good construction practices; clear commu- nication among contractors, supervisors, community, and the MoSSaiC core unit; and timely disbursement of funds for procurement of materials and payment of contractors/laborers 4. Sign off on completed construction Construction • Identify outstanding works completed and signed off on • Arrange for any necessary repairs or minor modifications • Sign off on completed construction and pay withholding payments to contractors 1. Understand how new practices are adopted Assessment of aspects • Use the steps in the ladder of adoption and behavioral change model to identify of behavioral change communication and capacity-building needs in each community and in govern- to be addressed by ment communication and capacity-building • Understand stakeholder perceptions and the role of community participation activities 2. Design a communication strategy Communication • Review existing resources and methodologies for designing a communication strategy strategy 8. Encouraging • Identify communication purposes and audiences Behavioral • Select forms of communication and design messages Change 3. Design a capacity-building strategy Capacity-building • Review knowledge into action approaches strategy • Identify levels of capacity, capacity requirements, and activities for building capacity 4. Plan for postproject maintenance Project maintenance • Understand the need for incorporating maintenance into drain design and project options planning 5. Map out the complete behavioral change strategy Map of capacity- • Map the agreed-upon behavioral change strategies and associated actions building strategies (continued) CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    3 9 TAB L E 1.11 MoSSaiC (continued) CHAPTER COVERAGE OUTPUT 1. Agree on key performance indicators (KPIs) for immediate project outputs List of project output • Develop and agree on a list of KPIs that comply with donor/government needs KPIs for evaluation and MoSSaiC output measures 2. Agree on KPIs for medium-term project outcomes List of project 9. Project • Develop and agree on a list of project outcome measures that allow evaluation of outcome KPIs for Evaluation landslide hazard reduction, project costs, and behavioral change evaluation 3. Undertake project evaluation Project evaluation • Agree on responsibilities for short- and medium-term data collection and the report project evaluation process • Carry out the evaluation Countries with small and vulnerable econo- disasters with respect to their capital stock mies, such as many SIDS and land-locked are all SIDS and LLDCs, such as Samoa and developing countries (LLDCs), have seen St. Lucia (UN 2009, 9). their economic development set back decades by disaster impacts. The countries Figure 1.24 shows the impact Hurricane with the highest ratio of economic losses in Allen (1980) had on the economy of St. Lucia. TA BLE 1 .1 2  Characteristics of MoSSaiC project locations in the Eastern Caribbean, 2004–10 FACTOR DESCRIPTION Region Eastern Caribbean—SIDS with high vulnerability to natural disasters (UNISDR 2009) Countries St. Lucia, Dominica, and St. Vincent and the Grenadines Slopes Slopes of 25–50 degrees, which had previously exhibited instability at low rainfall intensities (typically as low as 1 in 1 year 24-hour events) Slope material Often comprising deep residual soils over highly weathered volcanic bedrocks or conglomerates Communities Unauthorized urban communities—unregulated development, densely built, with poor construction quality; each community typically comprising 20–100+ houses Risk drivers Rainfall events triggering landslides on slopes with increased susceptibility to landslides due to natural and anthropogenic influences FI G U R E 1.22  Typical communities and risk drivers for MoSSaiC interventions a. Hillsides prone to landslides and b. Housing stock typical of vulnerable c. Density of unauthorized housing populated by unauthorized housing. communities. increases likelihood of property loss. 4 0    C H A P T E R 1 .   F O U N DAT I O N S : R E D U C I N G L A N D S L I D E R I S K I N CO M M U N I T I E S FI G U R E 1.2 3  Countries with damages from disasters exceeding 1 percent of GDP share of GDP (%) 10 8 6 4 2 0 St. Lucia Grenada St. Kitts & Nevis Samoa Nicaragua Maldives Mongolia Vanuatu Yemen, Rep. Dominica Virgin Islands Guyana Burkina Faso Tonga Belize Madagascar Jamaica El Salvador Bahamas Bangladesh Zimbabwe Fiji Bolivia Mauritius Nepal Source: World Bank 2010b. FI G U R E 1.24  Impact of Hurricane Allen illustrated by figure 1.25, which shows a com- (1980) on the economy of St. Lucia munity in Dumsi Pakha, a small village located in the Darjeeling Hills, in the Lesser Himalaya. constant 2000 $, millions It is a hillside with high-density housing and 3,000 no provision for surface water management. 2,500 without e ect With an average elevation of 2,050 m, the area of disasters 2,000 has steep slopes and loose topsoil, giving rise to 1,500 frequent landslides over recent years. In spite with e ect of disasters of strict rules and regulations, homes continue 1,000 to be constructed in the area (Savethehills 500 2011). This environment is thus very similar to 0 those of the Eastern Caribbean. –500 –1,000 1970 1980 1990 2000 F IGUR E 1. 2 5  MoSSaiC is applicable to Source: UNISDR 2009. many locations outside the Eastern Caribbean The dark brown line shows the actual cumula- tive net capital formation for 1970–2006; the light brown line shows the projected cumula- tive net formation without economic losses from disasters. The main MoSSaiC principles and methods developed in the Eastern Caribbean context are applicable in other parts of the humid trop- ics with comparable landslide risk drivers. The Source: Praful Rao, Savethehills, Kalimpong, India. potential breadth of MoSSaiC applicability is CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    4 1 1.5 STARTING A MOSSAIC Thus far, MoSSaiC has been applied at the INTERVENTION small scale (section 1.4.6), using the definitions of Binswanger-Mkhize, de Regt, and Spector (2009) shown in table 1.13. MoSSaiC may Starting a MoSSaiC intervention requires iden- potentially be scaled up to national and tification of the scale and scope of the project, regional levels, while retaining community- creation of teams to deliver the program, selec- scale effectiveness and innovation. Several tion of communities in which interventions are potential issues need to be recognized when to be made, generation of a project logframe, considering such scale-up (table  1.14), and and understanding of the issues involved in Easterly’s “testâ€? should be taken into account: making the project sustainable. This book is designed to provide a flexible The sad part is that the poor have had so little blueprint for establishing a MoSSaiC interven- power to hold agencies accountable that the tion. While the majority of the text is, of neces- aid agencies have not had enough incentive sity, devoted to the details of delivering on- to find out what works and what the poor the-ground mitigation measures, equal weight actually want. The most important sugges- should be given by the MCU to evidence of tion is to search for small improvements, performance of the measures (physical and then brutally scrutinize and test whether the cost-effectiveness, introduced in section 1.4.4), poor get what they wanted and were better and to the longer-term outcomes and behav- off and then repeat the process (Easterly ioral change achieved as a result (table 1.9 and 2006, 180). figure 1.21). 1.5.2 Define the project teams and 1.5.1 Define the project scale stakeholders Initiating a new form of community-based Three types of team project can rarely be done in one fell swoop at the national level; the numbers are just too To build the necessary teams involves iden- daunting (table 1.13). Rather, starting with a tifying colleagues from all relevant stake- few pilot projects should result in a locally rel- holder groups with a keen interest in pro- evant set of logistics, operational and training moting MoSSaiC and who have the requisite books, materials, and tools that can then be expertise. Three types of team need to be used to support a wider program. built: TA BLE 1 .1 3  Magnitudes of scale-up SMALL-SCALE LCDD PILOT PHASE OF SUCCESS SCALE-UP SCALED UP 1 district/administrative 1–4 districts/administrative All districts/administrative center centers centers 1–4 subdistricts 6–24 subdistricts All subdistricts 5–20 community groups  100–1,000 community groups  Tens of thousands–hundreds of thousands of community groups < 50 community projects 100–2,000 projects Hundreds of thousands of projects < 50,000 people 100,000–1 million people Many million people Source: Binswanger-Mkhize, de Regt, and Spector 2009. Note: LCDD = local- and community-driven development. 42    C H A P T E R 1 .   F O U N DAT I O N S : R E D U C I N G L A N D S L I D E R I S K I N CO M M U N I T I E S TAB L E 1.14  Issues to consider when scaling up MoSSaiC ISSUE COMMENT “Sometimes things work for idiosyncratic reasons—a charismatic (and literally Replication may irreplaceable) leader or a particular (and unrepeatable) crisis that solidifies support not be possible for a politically difficult innovation. So one-time successes may not be replicableâ€? (World Bank 2004, 108). While certain elements of the approach may provide sound guidance, there are Experimentation limits to the standardization of any approach. “Experimentation, with real learning may be necessary from the experiments, is the only way to match appropriate policies with each country’s circumstancesâ€? (World Bank 2004, 108). A social franchise model is recognized as a possible suitable scaling-up approach in which a close dialogue is maintained between countries undertaking the approach Adopting a (franchisee) and the originators (franchisors). This aims to capture the advantage of recognized standardization and experimentation referred to above. To that end, the franchisees approach to (whose role is to implement the approach locally) are decentralized and largely scale-up may give autonomous. “A pilot project that is developed by the franchisor is replicated by a value added number of franchisees subject to defined guidelines. These are usually laid down in the form of a book and communicated to the franchisees through training offered by the franchisorâ€? (Ahlert et al. 2008, 23). • MoSSaiC core unit. This typically com- leaders. Community leaders can play a cata- prises local government agency expert lytic part in projects: conveying the vision practitioners and project managers in the to other residents and coordinating with fields of civil engineering, social develop- government teams. In some cases, an indi- ment and community outreach, emergency vidual with particular skills and an under- management, financial management, water standing of the project’s technical aspects resource management, and agriculture. The can act as a catalyst and raise awareness of MCU acts as the bridge between regional slope management issues in his or her own and national initiatives for risk reduction, and other communities. Such understand- the government technical and field task ing establishes appropriate consultative teams, and the communities. To be effective channels at the start of the intervention, in its role, the MCU must have an under- and ensures that expectations are appropri- standing of the relational nature of the ately set in terms of outcomes and likely community—its key players, leaders, beneficiaries. groups, and elected representatives; and its relationships with government, especially The teams, together with their roles and in terms of previous social intervention responsibilities, are fully defined in chapter 2. activities. Teams require an organizational structure • Government task teams. Teams will to both manage a process and deliver outputs include a number of groups of specialists and outcomes. Structuring an MCU, and cap- and practitioners such as GIS technicians, turing existing government and community field survey technicians, community liaison individuals within country, is a deliberate officers, local engineers, and planning offi- attempt to recognize that cers. The leaders of the various government …a Bureaucracy works best where there is task teams are likely to be MCU members. high feedback from beneficiaries, high incen- tives for the bureaucracy to respond to such • Community task teams. The three main feedback, easily observable outcomes, high constituents from the community will be probability that bureaucratic effort will residents, contractors, and community translate into favourable outcomes, and com- CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   43 petitive pressure from other bureaucracies • Analyzing—identifying the strengths and and agencies (Easterly 2002, 4). weaknesses of existing policies and service and support systems Stakeholder involvement • Setting objectives—deciding and articulat- MoSSaiC requires a broad and cohesive stake- ing what is needed holder base, and one that deliberately encour- ages community participation. The MCU • Creating strategy—deciding, in pragmatic should identify all potential stakeholder terms, directions, priorities, and institu- groups and shape the management structure tional responsibilities according to the local context. Table 1.15 indi- • Formulating tactics—developing or over- cates the likely stakeholders and their respec- seeing the development of project policies, tive involvement. specifications, blueprints, budgets, and Given the community basis of MoSSaiC, it technologies needed to move from the pres- is important for the MCU to ent to the future • be clear on the purpose of participation, • Monitoring—conducting social assess- • know the value offered by community ments or other forms of monitoring of proj- engagement, ect expenditures and outputs • understand how the community can par- Community selection ticipate, and Communities can be prioritized and selected • anticipate any unintended consequences of by addressing the following questions using participation. available data: • Which communities have suspected land- Participation allows stakeholders to collab- slide problems? oratively carry out a number of activities in the program cycle, including the following (World • Are these communities vulnerable in pov- Bank 1998): erty terms? TAB L E 1.15  Likely stakeholders and their potential involvement in a MoSSaiC intervention STAKEHOLDER INVOLVEMENT Householders • May be directly at risk from landslides and/or contribute to the hazard due to adverse slope management practices • May have important knowledge of localized slope processes and slope history • May have skills in drain construction Landowners Will need to be consulted if drainage structures are to be built and access rights required Community representatives May represent a community project committee and become advocates for the project Government agency May have a formal role in project initiation and implementation representatives Residents of other potential May perceive that their needs are greater or have skills or experiences to share communities NGOs or similar agencies May be coordinating with the same government and community representatives on a working in the same community different, but potentially related, project Donors May have instigated the approach but whose representatives may be seen as remote partners Elected parliamentary represen- May have lobbied in the community selection process and subsequently become advocates tatives for the approach Media representatives Will cover project roll-out and can choose how they portray the delivery, purpose, and impact 4 4    C H A P T E R 1 .   F O U N DAT I O N S : R E D U C I N G L A N D S L I D E R I S K I N CO M M U N I T I E S • Can the landslide hazard be confirmed? 1.5.4 Establish a project logframe • Is the intervention likely to be cost-effec- Establishing a project framework at inception tive, and does it fit the project scope? is an important starting point for the MCU in Typically, there will be a range of data and preparing the overall project design. A log- political factors that need to be assimilated by frame is a widely used document that provides the MCU in prioritizing and selecting commu- such a structure; it is essentially a project nities. Chapter 4 details a process that can be design checklist, and is a recognized frame- used for community selection. work among donor agency and government stakeholders. The MCU should create a 1.5.3 Adhere to safeguard policies MoSSaiC logframe at the start of the project Implementation of risk reduction itself carries and refer to it throughout. potential risks. Safeguard policies seek to pre- The logframe analysis can be used as an itera- vent and mitigate undue harm to people and tive, dynamic tool throughout the project their environment by providing guidelines for cycle, rather than as a one-off exercise. It can the identification, preparation, and implemen- be used for identifying and assessing activi- tation of programs and projects. The effective- ties, preparing the project design, appraising project designs, implementing approved ness and development impact of DRR projects projects and monitoring, reviewing and eval- can be substantially increased as a result of uating project progress and performance attention to such policies. These policies have (AusAID 2000). In the words of DFID often provided a platform for the participation (c. 2003, 3), “it is a living document: it should of stakeholders in project design and have be reviewed regularly during approach and been an important instrument for building project implementationâ€? (Benson and Twigg 2004, 87). ownership among local populations. Once teams are in place, stakeholders iden- The best logframes are designed with stake- tified, and a project logframe developed (sec- holder involvement to ensure that everyone tion  1.5.4), safeguard policies should be concerned understands the relationship sourced, developed, and adapted as necessary between inputs and the desired outputs, out- for the local context; they should then be comes, and impact. Both direct beneficiaries agreed upon and disseminated. While all those (primary stakeholders) and project partners involved in a MoSSaiC intervention should be (secondary stakeholders) should be involved aware of safeguard policies, they are of special in formulation of the project logframe. relevance to the MCU (in its managerial role; The logframe should be simple and concise see section 2.3.2) and to those involved in con- with the project goal, purpose, and outputs struction (see section 7.7.1). specified in full and anticipated activities sum- Practices for safeguards will vary depend- marized. It should be a stand-alone document ing on the country, donor agency, and govern- explaining the intentions of the project com- ment context. A useful starting point is the prehensively and at a glance, and should be no Safeguard Policies of the World Bank (2011). more than four pages long. Table 1.17 details a The MCU must ensure that the project com- sample project logframe, presented in the plies with any relevant safeguards and proto- form of a matrix. cols stipulated by a donor or the government, In this book, the detailed steps and outputs or dictated by good practice, although it is rec- identified in section 1.4.5 (and replicated at ognized that formal responsibility for compli- the beginning of each chapter) will be helpful ance may well lie elsewhere. Table 1.16 illus- in creating a logframe. Chapter 9 identifies trates some typical safeguards that might typical key performance indicators, overall apply. This list should not be viewed as com- project outputs, and longer-term outcomes prehensive and is not intended as a substitute that might be included in a MoSSaiC project for binding policies and procedures. logframe. CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    4 5 TA BLE 1 .1 6  Typical safeguard policy considerations SAFEGUARD DESCRIPTION Evaluates a project’s potential environmental risks and impacts in its area of influence; examines project alternatives; identifies ways of improving project Environmental selection, siting, planning, design, and implementation by preventing, minimizing, assessment mitigating, or compensating for adverse environmental impacts and enhancing positive impacts; and includes the process of mitigating and managing adverse environmental impacts throughout project implementation. Is there the potential to cause significant conversion (loss) or degradation of natural habitats? It must be expected that donors would not support projects that would lead to the significant loss or degradation of any critical natural habitats, i.e., natural habitats that are • legally protected, • officially proposed for protection, or Natural habitats • unprotected but of known high conservation value. In other (noncritical) natural habitats, projects might be allowed to cause significant loss or degradation only when • there are no feasible alternatives to achieve the project’s substantial overall net benefits; and • acceptable mitigation measures, such as compensatory protected areas, are included in the project. Is the project situated in a disputed area? Has landownership been established and permission granted in writing if required? Projects in disputed areas may affect the relations between a wide range of stakeholders and claimants to the disputed area. Therefore, it is likely that donors Disputed areas and governments would only finance projects in disputed areas when there is no objection from the other claimant to the disputed area. It is possible that special circumstances of the case support financing, notwithstand- ing the objection. In this case it is to be expected that a transparent policy details the precise nature of such special circumstances. Involuntary resettlement can be defined not only as physical relocation, but any loss of land or other assets resulting in (1) relocation or loss of shelter; (2) loss of assets or access to assets; (3) loss of income sources or means of livelihood, whether or not the affected people must move to another location. Involuntary resettlement is triggered in situations involving involuntary taking of land and involuntary restrictions of access to legally designated parks and protected areas. A safeguard policy would aim to avoid involuntary resettlement to the extent Involuntary feasible, or to minimize and mitigate its adverse social and economic impacts. resettlement • A safeguard policy would promote participation of displaced people in resettle- ment planning and implementation, and its key economic objective would be to assist displaced persons in their efforts to improve or at least restore their incomes and standards of living after displacement. • A safeguard policy would prescribe compensation and other resettlement measures to achieve its objectives and require that borrowers prepare adequate resettlement planning instruments prior to donor appraisal of proposed projects. Cultural resources are important as sources of valuable historical and scientific Physical cultural information, as assets for economic and social development, and as integral parts of resources a people’s cultural identity and practices. The loss of such resources is irreversible, but fortunately, it is often avoidable. Source: World Bank 2011. 4 6    C H A P T E R 1 .   F O U N DAT I O N S : R E D U C I N G L A N D S L I D E R I S K I N CO M M U N I T I E S TAB L E 1.17  Example of a logframe format IMPORTANT RISKS AND PROJECT SUMMARY MEASURABLE INDICATOR MEANS OF VERIFICATION ASSUMPTIONS GOAL: Higher-level goal to which What external conditions are the project will contribute (such as essential for the project to Millennium Development Goals, make its expected contribu- poverty reduction). Note that the tion to the goal goal is not intended to be achieved through the project alone. PURPOSE: What will be achieved? The quantitative measures Sources of information Risks and external conditions Consider what will change, who will or qualitative evidence by that will be used to assess on which the success of the benefit and how, and the impact the which achievement of the the indicator(s). These project depends project will have in relation to the purpose will be judged; should be numbered to aims. This should be one statement. these should be numbered. correspond with indicator numbering. OUTPUTS: Identify the set of SMART (specific, measur- Sources of information to Risks—factors not within the realistic measurable outputs able, achievable, relevant, be used to identify control of the project that (outcomes/results) that will be and time-bound) indicators whether the indicators may restrict the achievement needed to work together to ensure must be included for each have been met. These of the outputs or of the the achievement of the purpose. output. Preparing useful should be numbered to purpose, even if all the (Outputs are not simply completed and time-bound indicators correspond with indicator outputs were achieved activities—if training is the activity, is an essential element for numbering. then a completed training session is effective monitoring and simply a completed activity; reporting. These should be behavioral change as a result of numbered to correspond receiving the training would be an to output numbering. output.) Normally, projects have four or five outputs. These should be numbered. ACTIVITIES: These are the tasks to A summary of the project budget and other key inputs and resources to complete the be completed to produce the activities outputs. They should be given numbered to correspond to the relevant output. Source: DFID n.d. 1.5.5 Brief key leaders of people to champion the approach. This is Readers should use the information in this the starting point for chapter 2. chapter to initiate discussions and brief strate- gically placed policy makers, senior project MILESTONE 1: managers, and local experts. Effective commu- nication of the MoSSaiC vision and founda- Key catalytic staff briefed on tions will help establish potential membership MoSSaiC methodology of the MCU, and thus help secure the support CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   47 1.6 RESOURCES 1.6.1 Who does what CHAPTER TEAM RESPONSIBILITY ACTIONS AND HELPFUL HINTS SECTION Policy/decision • Become familiar with ex ante DRR approach 1.3 makers, funding Understand DRM Helpful hint: Be aware of recent influences on DRM policy agency (section 1.3.3). • Become familiar with MoSSaiC approach 1.4 Understand MoSSaiC Helpful hint: Be aware of unique aspects of MoSSaiC (section 1.2.1). • Identify government departments, agencies and other 1.5.2 Understand local institutional organizations that could contribute to community-based DRM context landslide risk reduction Identify individuals who have the • Brief key individuals on MoSSaiC 1.5.5 potential to contribute to MoSSaiC MCU • Become familiar with MoSSaiC approach 1.3; 1.4 Upon appointment, understand DRM and the MoSSaiC approach Helpful hint: Be aware of unique aspects of MoSSaiC (section 1.2.1). Government task • Become familiar with MoSSaiC approach 1.3; 1.4 teams Upon appointment, understand DRM and the MoSSaiC approach Helpful hint: Be aware of unique aspects of MoSSaiC (section 1.2.1). When community task teams • Communicate the MoSSaiC vision to community task 1.4 have been appointed, inform the teams team members of MoSSaiC Community task • Become familiar with MoSSaiC approach 1.3; 1.4 teams Upon appointment, understand DRM and the MoSSaiC approach Helpful hint: Be aware of unique aspects of MoSSaiC (section 1.2.1). 1.6.2 Chapter checklist SIGN- CHAPTER CHECK THAT: TEAM PERSON OFF SECTION 99Existing local landslide risk reduction activities identified 1.3 99MoSSaiC approach understood 1.2.1; 1.4 99Relevant stakeholder groups and individuals identified and briefed 1.5.2 99All necessary safeguards complied with 1.5.3 99Milestone 1: Key catalytic staff briefed on MoSSaiC methodology 1.5.5 1.6.3 References Ahlert, D., M. Ahlert, H. V. D. Dinh, H. Fleisch, T. Heußler, L. 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(1992, 4) CHAPTER 2 Project Inception: Teams and Steps 2.1 KEY CHAPTER ELEMENTS 2.1.1 Coverage This chapter identifies existing within-coun- responsible for project implementation and try capacity to build the MoSSaiC (Manage- defines typical project steps. The listed groups ment of Slope Stability in Communities) teams should read the indicated chapter sections. AUDIENCE CHAPTER F M G C LEARNING SECTION    How to start the project with the MoSSaiC core unit: mission, members, 2.2, 2.3 roles, responsibilities    How to select the government task teams; their roles and responsibilities 2.4    How to select the community task teams; their roles and responsibilities 2.5    Main MoSSaiC project steps for each team 2.6, 2.7 F = funders and policy makers  M = MoSSaiC core unit: government project managers and experts  G = government task teams: experts and practitioners  C = community task teams: residents, leaders, contractors 2.1.2 Documents CHAPTER DOCUMENT TO BE PRODUCED SECTION Documents specifying team structures and personnel, and defining roles and responsibili- 2.6 ties, with sign-off by representatives from the relevant government agencies Project operations manual or equivalent specifying steps and associated milestones for 2.6, 2.7 implementation 55 2.1.3 Steps and outputs STEP OUTPUT 1. Establish the MoSSaiC core unit (MCU); define and agree on key responsibilities MCU formed • Identify available experts in government • Form the MCU and establish communication lines with government 2. Identify and establish government task teams; define and agree on key Government task responsibilities teams formed • MCU to identify individuals from relevant ministries to form government task teams (mapping, community liaison, engineering, technical support, communi- cations, advocacy) • Define roles and responsibilities of the teams 3. Identify and establish community task teams; define and agree on key responsi- Community task bilities* teams formed • MCU to identify individuals from selected communities to form community task teams (residents, representatives, construction teams) • Define roles and responsibilities of the teams 4. Agree on a general template for project steps Project steps • Review project step template and amend as necessary determined and responsibilities • Assign team responsibilities to relevant project steps; confirm project mile- assigned stones *This can only be done once communities have been selected for a MoSSaiC project; see chapters 4 and 5. 2.1.4 Community-based aspects coordination of a diverse team including community residents, field and mapping An important part of this chapter is the identi- technicians, engineers, contractors, and fication of the members of community-based social development officers. A strong, multi- task teams (community residents, representa- disciplinary MoSSaiC core unit (MCU) tives, contractors, and landowners), which are needs to configure and manage specific proj- an integral part of the wider MoSSaiC team. ect steps, roles, and responsibilities and Without the full recognition and involvement thereby attempt to reproduce the success of these teams, the project would have no factors outlined in table 2.1. grounding in the communities, the commu- nity-based mapping process and landslide The role of the MoSSaiC core unit hazard assessment would be incomplete (or incorrect), and there would be no sustainable A central element of MoSSaiC is the develop- delivery mechanism for appropriate landslide ment of a cross-ministry team of government hazard reduction measures. managers and expert practitioners. This book refers to this team as the MCU; different coun- tries may chose to give the team another name. 2.2 GETTING STARTED The MCU will perform the following: • Identify clear project steps that will effec- 2.2.1 Briefing note tively deliver on-the-ground landslide haz- An integrated approach to landslide risk ard reduction measures in communities in management the form of surface water drainage To deliver landslide risk reduction measures • Identify and draw on local expertise to in vulnerable communities requires the implement project steps by establishing 5 6    C H A P T E R 2 .   P RO J E C T I N C E P T I O N : T E A M S A N D ST E P S TAB L E 2 .1  Key characteristics of highly successful social development projects CHARACTERISTIC Quality participation from all stakeholders Participants given responsibility for structuring their project involvement Participants, especially beneficiaries, involved in project design Project team composition and team continuity Integrated attention to social development themes affecting project implementation Analysis of socially relevant aspects of the project Source: IEG 2005. appropriate task teams at the government • Project steps and milestones should be and community levels agreed upon. • Ensure that government and donor proto- 2.2.3 Risks and challenges cols are followed at every step Appropriate objectives • Ensure that appropriate landslide assess- The concepts contained in this book should be ment, community selection and engage- adapted by each country to reflect the local ment, and contracting procedures are fol- risk profile and government and community lowed contexts. In particular, objectives should not • Clearly communicate task team roles and be either overly ambitious or open-ended responsibilities so each individual under- since this can weaken accountability, prevent stands his or her specific tasks and contri- the delivery of appropriate mitigation mea- bution within the wider project sures, and reduce the likelihood of adoption of good slope management practices by govern- • Develop and convey the vision (and poten- ment and communities alike. tial) for reducing landslide risk in vulnera- ble communities in a way that is relevant to Taking time to identify MCU membership the teams and wider audiences. The cross-disciplinary MCU is the core mana- gerial structure of MoSSaiC. Identifying indi- The breadth of activities involved in viduals within government and related agen- MoSSaiC demands that roles and responsibili- cies who are committed to the concept of ties be very clearly identified and agreed upon. formulating a community-based approach to This chapter is designed so the MCU can be landslide risk reduction is the starting point for built and equipped to complement existing any MoSSaiC project. Sufficient time should be government structures. spent talking to a broad range of interested par- ties and individuals to identify MCU team 2.2.2 Guiding principles members who share the MoSSaiC vision and The following guiding principles apply in have relevant positions, skills, or expertise. starting up the MoSSaiC project: Avoiding parallel structures • An MCU should comprise a membership The establishment of the MCU and its associ- that is approved of and respected by gov- ated task teams should not create parallel ernment and within communities. structures that compete with or undermine • Clear, widely known responsibilities should existing institutional structures or democrati- be established for the MCU and each cally elected local or national governments MoSSaiC task team. (Mansuri and Rao 2003). CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    5 7 Fully developing and engaging with all task teams • Inadequate attention to project safeguards Task teams should be identified and appropri- (especially if there are issues of landowner- ately staffed for each project step to ensure that ship relevant to any proposed construction no individual or group is overburdened or or required access) required to take on tasks exceeding expertise. Relevance of project documents Clear, consistent, and frequent communica- tion will maintain momentum and commit- Avoid producing documents that are unlikely ment from individuals who may have other to be used and read. Instead, focus on develop- responsibilities. The form this communication ing a suite of documents that provide sound takes needs to be agreed upon at the start of records for subsequent project impact analy- the project. Whether regular communication sis, enable teams to undertake their tasks, and is by e-mail or briefing meetings, for example, serve public awareness and media initiatives. will very much depend on local practices. Creating a platform for behavioral change Realistic project time frames Urban development can generate landslide risk; conversely, landslide risk can affect devel- Project initiators are frequently overly opti- opment. At a community level, each household mistic about the schedule for implementing can inadvertently contribute to landslide risk multidisciplinary projects (see, e.g., IEG or, with good slope management practices, 2000). Because MoSSaiC integrates govern- play an important role in its mitigation. Gov- ment and community, and focuses on delivery ernment projects and policies can also either of physical landslide reduction measures in increase or reduce landslide risk at the com- communities, it is particularly important that munity, municipal, or national scale. Creating expectations of project timing and outcomes a platform for behavioral change in communi- are set realistically. This is not just to avoid ties and governments is an important part of unrealized expectations and having to deal the MoSSaiC vision, and it is best achieved by with the consequences (particularly in com- engaging with the community from start to munities), but for the more positive reason finish and by using existing government staff that being seen to deliver the project on time to form the MCU. In this way, landslide hazard and on budget is likely to encourage behavioral reduction measures can be delivered on the change. Small successes build confidence and ground, and behavioral changes be achieved as lead to wider uptake. the community and government teams learn by doing. Quality of project management A lack good quality project management can 2.2.4 Adapting the chapter blueprint to lead to a variety of poor outcomes: existing capacity This chapter provides a flexible blueprint for • Inadequate project conceptualization and MoSSaiC project inception. Funders and pol- design (potentially resulting in loss of finan- icy makers, in conjunction with the MCU, cial or decision-making transparency, poor should adapt this blueprint to suit local capac- scientific justification of hazard reduction ity and institutional structures. measures, and inadequate design or con- Use the matrix opposite to determine exist- struction of hazard reduction measures) ing capacity to configure multidisciplinary • Poor quality construction (if site supervision community-based projects, and hence the is not scheduled sufficiently frequently) likely capacity for forming MoSSaiC teams. • Project interruptions and contractors not 1. Assign a capacity score from 1 to 3 (low to getting paid on time (if the funding stream high) to reflect existing capacity for each is not adequately managed) element in the matrix’s left-hand column. 5 8    C H A P T E R 2 .   P RO J E C T I N C E P T I O N : T E A M S A N D ST E P S EXISTING CAPACITY CAPACITY ELEMENT 1 = LOW 2 = MODERATE 3 = HIGH Community organization and Communities generally lack Some community organiza- Functioning community-based representation by leaders structures and leadership tional or leadership structures organizations and leadership Government-community Role nonexistent Government-community Well-developed government- liaison role liaison on informal/unstruc- community liaison role tured basis Previous community-based Little history of community- Some previous community- Good track record of projects based projects based projects, but outcomes delivering successful commu- not sustained nity-based projects Government experience in Little or no experience in Some community-based One or more agencies with implementing community- implementing community- works implemented by one or proven experience in imple- based works (construction) based works more government agencies menting community-based works with a range of donor/ government funding models Government experience in Little or no experience in Some community-based Experience in community- implementing community- implementing community- disaster risk management based disaster risk manage- based disaster risk manage- based disaster risk manage- projects, with main focus on ment projects, including ment projects ment disaster preparedness or hazard assessment and vulnerability reduction mitigation Coordination of multidisci- Community-based projects Some cross-ministry coordina- Well-integrated structures plinary community-based undertaken by a single tion on a project-by-project across government to projects implementing agency basis facilitate cross-ministry coordination Project safeguards Documented safeguards need Documents exist for some Documented safeguards to be located; no previous safeguards available from all relevant experience in interpreting and agencies operating safeguard policies CAPACITY LEVEL HOW TO ADAPT THE BLUEPRINT 1: Use this chapter The country needs to strengthen its capacity in order to initiate a MoSSaiC project and form the required in depth and as a teams. This might involve the following: catalyst to secure • Actively searching for a policy entrepreneur to start the process by which an MCU is formed support from other agencies as • Organizing cross-agency and cross-government department meetings to explain the MoSSaiC vision and appropriate the need to create an MCU 2: Some elements The country has strength in some areas, but not all. Elements that are perceived to be Level 1 need to be of this chapter will addressed as above. Elements that are Level 2 will need to be strengthened, such as the following: reflect current • If the government has experience in hazard mitigation using multidisciplinary teams but not at the practice; read the community level, it should identify agencies already working in communities that could be partners in a remaining elements MoSSaiC project. in depth and use them to further strengthen capacity 3: Use this chapter The country is likely to be able to form an MCU based on existing proven capacity. The following would as a checklist nonetheless be good practice: • Document relevant government experience in community-based hazard mitigation, project manage- ment, and related safeguards CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    5 9 2. Identify the most common capacity score risk reduction options, and then treatment of as an indicator of the overall capacity level. the risk. This requires the coordination of experts in the areas (and order) shown in 3. Adapt the blueprint in this chapter in accor- table 2.2. dance with the overall capacity level (see guide at the bottom of the previous page). A new way of building capacity A review of selected capacity assessment Forming the MCU from existing staff within methodologies can be found in UNDP (2006), governments and agencies is a sound way of and Venture Philanthropy Partners (2001, 84) seeking to build capacity within government. provides an example of a detailed capacity Initially, capacity is enhanced simply by pro- assessment framework for nonprofit organiza- viding the opportunity for government staff to tions. exercise their expertise in an innovative way and as part of a multidisciplinary team. This expertise is developed and increased through 2.3 ESTABLISHING THE MoSSaiC hands-on experience as the project progresses. CORE UNIT Successful implementation of landslide risk reduction measures in the first few communi- 2.3.1 Rationale ties encourages behavioral and policy changes within government. Integrated approach to a multidisciplinary The MCU thus becomes both a focus for problem building capacity and the means of building Typically, the management of landslide risk capacity in other teams, as it can provide the involves assessment of the risk, evaluation of following: TAB L E 2 .2  Typical landslide risk management project cycle TYPICAL PHASE REQUIRED SKILLS/EXPERTISE Landslide Identify the project: Determine the need for and interest in a risk landslide risk reduction project Management, financial, donor agency, management Formulate the project: Define the project scope, budget, aims, engineering/scientific project preparation objectives, and feasibility Identify the broad landslide risk: Identify the relative landslide Local community knowledge, mapping, susceptibility or hazard of different areas to different landslide types, data management, engineering/scientific and the relative vulnerability of the exposed communities Landslide Understand and estimate the specific landslide risk: For a specific risk community and hillside, identify the underlying landslide hazard Mapping, engineering/scientific, social assessment drivers and confirm the level of the hazard; confirm the relative science, economic exposure and vulnerability of the community Evaluate the risk: Compare with other risks and decide whether to accept or treat the risk Management, financial, engineering/ Identify disaster risk reduction options: Typical options are to avoid scientific or reduce the hazard, reduce vulnerability, or transfer the risk Plan the risk mitigation: Design the landslide hazard reduction Landslide Engineering/scientific measures (drainage to capture surface water and household water) risk reduction Implement risk mitigation: Issue and manage contracts and construc- Financial/contracting, community liaison, tion, raise public awareness engineering, supervision, construction Monitor and evaluate: Check project progress, problems, solutions, Management, community liaison, sustainability, impact engineering 6 0    C H A P T E R 2 .   P RO J E C T I N C E P T I O N : T E A M S A N D ST E P S • Project vision, in that it is distinctive and tially requires assistance, has the choice of designed to deliver physical outputs in helping or not helping. The aid recipient then communities has the choice of expending high or low effort in return. If the donor extends help and the • Task team coordination, to ensure that recipient contributes high effort, both donor appropriate within-government and gov- and recipient benefit significantly. However, ernment-community linkages are forged from the recipient’s perspective, it could be • Encouragement of capacity building and even better off by expending low effort increased resilience at the community level, (table 2.3). by engaging and involving communities Although the donor would prefer a situa- from the outset and in a transparent manner tion in which the recipient expended high effort, most cases result in a low effort (Ostrom • Focal point for collating and managing et al. 2001)—and consequent poor levels of information relating to landslides; such sustainability. Ostrom et al. (2001, 32) con- data are often dispersed across different clude that “it is the recipient whose actions ministries, agencies, and consultants make the difference in outcomes between sus- Sustaining good landslide management practice tainable and non-sustainable,â€? adding that a in-country more sophisticated donor would condition aid on participation by the recipient and make Certain projects may need high-level expertise efforts to give the recipient a sense of owner- to be brought into a country to supply special- ship. It is expressly these two features that ized engineering or scientific knowledge, usu- MoSSaiC seeks to capture through its team ally in terms of design but sometimes in site structure. investigation as well. Such external expert MCU and the policy entrepreneur role input should supplement rather than replace in-country project management and task Policy entrepreneurs “introduce, translate, teams. Focusing on a government-based MCU and help implement new ideas into public and local task teams is the best approach to practiceâ€? (Roberts and King 1991). Given the ensuring sustainable landslide risk manage- issues observed by Prater and Londell (2000) ment by and summarized in table 2.4, it is important to identify a policy entrepreneur to champion • creating a learning organization dynamic, MoSSaiC and support, or be part of, the MCU. • promoting cost-efficiency, MoSSaiC core unit mission • providing secure and sustainable govern- ment-community links, The MCU balances two elements that drive • providing for a coherent connection with and contribute to MoSSaiC project success: social development funds that can deliver projects at the community level, and TAB LE 2 . 3  The active Samaritan’s Dilemma • ensuring the optimal assimilation of appro- priate background data. RECIPIENT HIGH EFFORT LOW EFFORT Avoiding the “Samaritan’s dilemmaâ€? DONOR NO HELP 2,2 1,1 (SAMARITAN) HELP 4,3 3,4 A within-country MCU is a potentially sound way of avoiding the well-documented Samari- Source: Raschky and Schwindt 2009. Note: Subject preference (payoff) ranked from high (4) to low (1). The first tan’s dilemma. This problem, posed by number in each pair is the donor preference, the second is the recipient Buchanan (1977), revolves around the fact that preference. a donor, faced with a circumstance that poten- CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   61 TA BLE 2 .4  Landslide risk reduction issues that need to be offset by a policy entrepreneur ISSUE ROLE OF POLICY ENTREPRENEUR Political agendas are unstable over time Help keep disaster risk reduction on the agenda by being versed in the technical aspects of risk reduction, be a political expert, and have strong personal commitment Prevailing view of landslide risk may be that there Can counter this view with evidence that landslide is nothing that can be done about it risk reduction can work and pay Hazard mitigation and socioeconomic develop- Understand and promote a scientific and socio- ment are complex issues; simplistic policies can economic framework for landslide hazard have unintended consequences, while complex mitigation policies policies are difficult to develop • Top-down drivers and processes—such as prised of existing government staff; the com- the social, economic, and political impera- munity task teams will include both unpaid tive to arrest landslide risk accumulation; volunteers (community leaders and residents) and the requirements of project manage- and paid contractors from within the commu- ment and financing nity. Cultural norms and a lack of incentives • Bottom-up drivers and processes—such may constrain effective management of task as the community imperative to reduce teams, and there will usually be limitations in landslide risk and improve livelihoods, the power of a single agency to influence community participation in project design, behavioral change among a broader govern- and engaging workers from the communi- ment base. The MCU should devise a commu- ties to implement the intervention nication and engagement strategy that com- bines formal government protocols with a 2.3.2 MCU roles and responsibilities culturally sensitive approach to achieve proj- ect acceptance, staff and team integration, and The responsibilities of the MCU are pre- consensual ownership (World Bank 2003). scribed by its five core missions (figure 2.1). MCU roles and responsibilities in this regard are as follows: 1. Establish project scope and teams • Be familiar with MoSSaiC aims and scope The first mission of the MCU is to establish the vision, scope, and cross-disciplinary basis • Define local project scope in terms of land- of the project, and to identify task teams in the slide risk management needs with respect government and the community. to the appropriate application of MoSSaiC The MoSSaiC methodology needs to be • Adapt the MoSSaiC blueprint for building understood and correctly applied if the goal of task teams and defining project steps, roles, reducing landslide risk in communities is to be and responsibilities achieved. Each chapter in this book relates to a different phase of MoSSaiC implementation. • Own and champion the vision, and lead and The MCU should be aware of what is involved encourage the task teams in each of these project phases (encapsulated in the “Getting startedâ€? section in each mod- • Develop an effective strategy to facilitate ule) so as to correctly configure the project the task teams in their roles and establish the task teams. 2. Stay community focused Forming the MCU within-country delivers cost-effective project management. The MCU From the outset, the MCU will need to focus and government task teams should be com- on delivering landslide risk reduction mea- 62    C H A P T E R 2 .   P RO J E C T I N C E P T I O N : T E A M S A N D ST E P S FI G U R E 2 .1  Five missions of the MoSSaiC core unit a. Mission 1: Establish the vision, scope, b. Mission 2: Ground the project in c. Mission 3: Ensure good design of and cross-disciplinary basis of the project communities throughout the process to landslide hazard reduction measures, and identify task teams in government create a platform for behavioral change and the quality and completion of and communities. in both government and communities. construction. d. Mission 4: Create a culture of good e. Mission 5: Identify project safeguard requirements (relating to issues such as the slope management practice, and evaluate potential for involuntary resettlement following slope failure and house destruction project impact and sustainability in or for resolving landownership for drainage lines). partnership with communities and funding agencies. of slopes to landslides and vulnerability of sures in vulnerable communities. This focus communities to the impact of landslides will require the development of strategies to engage the community from the start and to • Ensure that the selected communities are maintain that engagement during landslide consulted on their priorities and the poten- hazard mapping and assessment, through the tial for implementing landslide hazard design process, during implementation, and in reduction measures the follow-up phases. • Ensure that appropriate community par- The government task teams should be ticipation approaches are used in selecting encouraged to work with community mem- community task teams, mapping landslide bers both formally and informally in order to hazards and drainage issues, designing a benefit from community knowledge of local drainage intervention, and conducting liai- slope processes and relevant community social son with residents during and after the structures. The community thus becomes the project locus both of activities and of hands-on expe- rience for the government and community • Establish a realistic community contracting task teams. process by which contracting and procure- The MCU roles and responsibilities in this ment are undertaken on behalf of or by the regard are as follows: community • Develop a community selection process • Ensure that contractors from the commu- that is justifiable in terms of susceptibility nity are engaged and supervised in the con- CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   63 struction of the landslide hazard reduction tices and the structures to enable them. The measures MCU is the core enabler in seeding project sustainability. • Encourage horizontal and vertical learning The MCU’s horizontal connection within through the hands-on involvement of task government, and its vertical integration with teams in the communities communities, provides the opportunity to 3. Maintain quality control develop a sustainable mechanism for embed- ding landslide risk reduction in practice and The effectiveness of any engineering or physi- policy. Building a team of senior civil servants cal measures constructed to reduce landslide and technical officers in this way has a poten- hazard depends on sound design, specifica- tial longevity that is generally not matched by tions, and construction. MoSSaiC involves elected political representatives. developing surface water drainage plans to MCU roles and responsibilities in this reduce landslide hazard and construction by regard are as follows: community-based contractors to achieve that • Create strong horizontal and vertical inte- goal. The MCU must therefore create strate- gration among senior civil servants, task gies for quality control and monitoring of the teams, and communities drainage design and implementation process; this responsibility is pivotal to the success of • Evaluate project outcomes (medium-term the measures. impacts and sustainability) as well as the MCU roles and responsibilities in this standard outputs required by donors regard are as follows: • Engage the community in assessing project • Select appropriately skilled task teams for successes and failures, in developing new mapping, landslide hazard assessment, and approaches and solutions, and in sharing drainage design experiences and expertise • Select experienced site supervisors • Promote the approach based on physical demonstration of good slope management • Establish an appropriate community con- practices, using project evaluations to tracting process and oversee the supervi- develop an evidence base for raising aware- sion of contractors ness and for leveraging further funding 4. Evaluate the project and develop sustainable • Provide regular updates to key senior civil practices servants and engineers, using photos, site visits, and short presentations or reports The success of the MoSSaiC project should not be measured simply in terms of the quality • Find a niche for the approach within the and quantity of immediate outputs (such as most appropriate government ministry or the length of drains built, number of house- agency holds benefiting, or money spent on employ- 5. Adhere to safeguards ing local contractors), but in terms of medium- term impact and sustainability (outcomes). The MCU must ensure that the project com- The MCU should thus monitor and evaluate plies with relevant safeguards and protocols the project beyond its immediate outputs. The stipulated by a donor or by the government or observations and experiences of the commu- dictated by good practice (section  1.5.3), nity are a vital resource in this regard. although it is recognized that formal responsi- The sustainability of the project is bility for compliance may well lie elsewhere. reflected in the degree of uptake by commu- Table 1.16 (chapter 1) illustrates some typical nity and government teams—the creation of safeguards that might apply. These should not a culture of good slope management prac- be viewed as comprehensive and are not 6 4    C H A P T E R 2 .   P RO J E C T I N C E P T I O N : T E A M S A N D ST E P S intended to be a substitute for binding policies projects. In a survey of the World Bank Devel- and procedures. opment Research Group, Mansuri and Rao MCU roles and responsibilities in this (2003) found that projects are often under- regard are as follows: taken with young, inexperienced facilitators whose incentives are not aligned with the best • Be fully conversant with the safeguards that interests of the community. This finding rein- apply to the project forces the critical role of the MCU and the • Communicate safeguards and processes for nature of its membership. compliance to relevant stakeholders • Keep a record of compliance MILESTONE 2: 2.3.3 MCU membership MoSSaiC core unit formed; key responsibilities agreed on and MCUs will vary in structure from country to country. Typically, members might be drawn defined from the following government departments, ministries, and agencies: • Public works 2.4 IDENTIFYING THE • Social development GOVERNMENT TASK TEAMS • Planning • Finance Part of the MCU’s first mission is to develop • National emergency organization teams dedicated to specific project tasks that • Statistics and census will ensure the delivery of appropriate physi- • Agriculture cal measures to reduce the landslide hazard. • Water and sewerage company Identification and initial engagement of Higher education and community colleges task team members will probably be an itera- (where there is relevant technical expertise tive and consultative process in conjunction that would be of value) may also contribute with the development of specific project steps. MCU members. In many cases, MCU members themselves Members selected should be fully conver- may be the most appropriate people to con- sant with and supportive of the MCU mis- tribute to or lead a particular task team. sions, roles, and responsibilities as outlined Each MCU member will need to identify above. They should be committed to deliver- and consult with expert practitioners (engi- ing landslide risk reduction measures using an neers, officials, and technicians) in their interdisciplinary, community-based approach. respective ministries to MCU members need to be able to command • identify motivated, knowledgeable, and respect from the communities, government, skilled individuals who want to contribute donors, and media (Anderson and Holcombe to the overall vision of achieving landslide 2004, 2006a, 2006b; Anderson, Holcombe, hazard reduction in communities; and and Williams 2007). MCU members need to stay fully engaged • consult with these individuals to identify throughout the project; if they do not, believ- cross-ministry collaborations and specific ing that the project has been established and is steps that they (as part of the ministry or to some degree running itself, project outputs agency) would need to undertake for proj- will suffer as a consequence. ect success. Qualitative evidence suggests that the role of project facilitators (MCU members in this Table 2.5 provides guidance on factors rele- case) is key to the success of community-based vant to the team selection process. CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    6 5 TAB L E 2 .5  Government task team selection factors FACTOR COMMENT Team size Typically, each government task team consists of about three individuals who display commitment to the vision. With six task teams, this totals about 18 government task team members in all. Team leaders may also be part of the MCU. Financial Experience has shown that it is not necessary for the respective government departments/agencies from compensation which the team members were drawn to receive financial compensation. Such a circumstance can be seen as increasing ownership of the vision. Time Depending on the scale of the intervention, it is unlikely that any team member role will, on average, be full commitment time. However, there may be periods when the individual is working full time for a few days. Convening of MCU members, having been chosen with regard to their respective specialization (section 2.3.3), search for team members and identify potential task team members. This process will entail both taking advice on suitable members as well as discussing opportunities with potential individuals. Membership In establishing the teams, it may be useful to achieve a mix of middle-management members (to deliver composition skills) combined with a modest number of more senior officials to drive policy acceptance. Housing of the It is appropriate to seek an office location for the MCU (perhaps a ministry office or a relevant agency in MCU which there is administrative support and in which there may be a top-level advocate for MoSSaiC). This helps demonstrate government support for the MCU and assists in project implementation. This section identifies typical areas of proj- enced task team leaders will need to take ect activity for which motivated and experi- responsibility (table 2.6). The task team leader TAB L E 2 .6  Task teams and guidance notes TYPICAL EXPERIENCE/POSITION OF CHAPTER TEAM MAIN TASK TASK TEAM LEADER SECTION Mapping Produce high-resolution maps for landslide Geographic information system (GIS), hazard assessment planning, and census officials 2.4.1 Community Develop community prioritization method Community development 2.4.2 liaison with mapping team Landslide Map landslide and drainage hazard, advising Scientists or engineers with expertise in assessment and the MCU of the appropriateness of the landslide risk assessment and hydrology GOVERNMENT- engineering MoSSaiC approach and overseeing the Civil engineers, especially with expertise 2.4.3 BASED preparation and letting of work packages in drainage, environmental engineering, bioengineering, design, and contract management Technical Site survey work and site supervision GIS, census, computing, surveying, support materials laboratory technicians, 2.4.4 supervision of works Communications Support the MCU in raising public awareness Media, public relations 2.4.5 Advocacy Engage with other decision makers and the Elected officials, funding agency represen- media to explain the MoSSaiC vision and its tatives 2.4.6 practical implementation Residents Assist all government teams on the ground in Residents, community leaders, and groups 2.5.1 COMMUNITY- their community BASED Community Provide detailed community context to the Community-elected officials 2.5.1 representatives MCU and other task teams Construction Community contractors provide knowledge Contractors 2.5.2 of local practices and undertake the works 6 6    C H A P T E R 2 .   P RO J E C T I N C E P T I O N : T E A M S A N D ST E P S will need to work closely with the MCU to important to identify the ministry with the design the project steps and build the team. most skilled individual(s) and the main reposi- Each task team may comprise individuals from tory of digital maps (such as topography, soils, other ministries with the necessary skills to geology, housing/landownership, and land undertake the assigned tasks. This informa- use) and aerial images. The ministry responsi- tion is provided as guidance only; specific cir- ble for planning is often the most appropriate cumstances may dictate variations depending host agency for this team. However, other on the local roles held by individuals in a par- ministries may be able to contribute data and ticular country. expertise in specific areas such as census information relating to poverty and the vul- 2.4.1 Mapping task team nerability of communities. Consider including The key responsibilities of the mapping task representatives from such groups on the team team are as follows: to ensure optimal coordination of both data assimilation and presentation. • Integrate any available spatial data on pov- erty and landslide susceptibility to support 2.4.2 Community liaison task team the process of identifying and prioritizing The key responsibilities of the community liai- communities for landslide risk reduction son task team are as follows: • Produce high-resolution maps of selected • Coordinate with the mapping team to communities to serve as the basis for the develop a transparent method for prioritiz- community-based mapping of slope fea- ing vulnerable communities tures, landslide hazard, and proposed drain locations. • Identify for the mapping team any social surveys or other data that would be helpful There may be many government depart- in the prioritization process ments that make use of geographic informa- • Coordinate with communities to identify tion system (GIS) technology (figure 2.2). It is community representatives • Act to moderate political or other motives FI G U R E 2 .2  Mapping team from a national for selecting certain communities, commu- disaster management agency demonstrates GIS software to MCU team leader nity representatives, or contractors • Coordinate with community residents and representatives throughout the project (fig- ure  2.3)—organizing informal and formal meetings and any public awareness materi- als that might be relevant • Bring knowledge of how the community works to the MCU • Ensure that the other teams engage with the community at each project stage. The role of the community liaison team is to ensure that communities are represented and engaged in the community selection process, mapping and intervention design, implemen- tation of measures, and any subsequent follow- up. This team may need to be part of other task team activities as the project progresses. CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    6 7 reducing landslide hazard in the commu- F IG U R E 2 . 3  Coordinating with Social nity Development Ministry and community residents on site • Engage and coordinate with additional spe- cialists (such as ground and quantity sur- veyors) • Design surface drainage measures, gener- ate work packages, and manage the con- tracting process to engage contractors from the community in construction • Ensure the quality of the works (to be man- aged by an experienced site supervisor). Successful reduction of landslide hazard depends on correct identification and assess- ment of the hazard, and design of appropriate 2.4.3 Landslide assessment and mitigation measures (surface drainage, in the engineering task team case of MoSSaiC). The landslide assessment The key responsibilities of the landslide and engineering task team should include at assessment and engineering task team are as least one civil or environmental engineer and follows (figure 2.4): any other government staff member with a background in and working knowledge of the • Direct the mapping team in the analysis of physical, geotechnical, and hydrological sci- available data on landslide susceptibility ences. and hazard to assist in community selec- In many countries, residents and govern- tion ment agencies will report landslide and drain- • Undertake community-based mapping of age issues to a specific government ministry. This ministry, which is often responsible for slope features; landslide hazard and drain- civil works, is likely to be the most appropriate age issues; and assessment of the location, one for fulfilling the key responsibilities out- magnitude, and cause of the hazard lined above. It will also have the necessary pro- • Appraise the MCU of the relevance and cesses and personnel to implement construc- potential cost-effectiveness of MoSSaiC in tion of landslide hazard reduction measures. F IG U R E 2 .4  Examples of landslide assessment and engineering task team responsibilities a. Assess different slope stabilization options. b. Design drain dimensions and alignment in complex topography. 6 8    C H A P T E R 2 .   P RO J E C T I N C E P T I O N : T E A M S A N D ST E P S 2.4.4 Technical support task team ate communications for use within the communities The key responsibilities of the technical sup- • Communicate project aims and progress to port task team (figure 2.5) are as follows: the wider public • Provide technical support to other teams in • Engage and manage media interest—from data acquisition, processing, and presenta- newspapers, radio, television—in the form tion of interviews of team and community mem- • Provide field support to other teams—e.g., bers, press releases, information on good undertaking ground or quantity surveys, or slope management practices, and other assisting in monitoring and evaluation coverage of the project. • Provide site supervision during implemen- The appropriate communication of land- tation of works slide issues, good slope management prac- • Suggest ways of working that would tices, and project aims and progress can improve on-the-ground implementation. encourage MoSSaiC uptake and sustainabil- ity. In many communities, the main form of Generally, skilled government technicians communication is word of mouth, often stay in a given role for long periods. Therefore, informed by some combination of commu- investment in their skills and inclusion in the nity meetings, radio, and television (fig- wider MoSSaiC project can encourage good ure 2.6). slope management practices to be embedded The MCU should decide on the message in government beyond the end of the project. it wishes to convey to the selected commu- nities and the public, and how that message is to be conveyed. The communications task FI G U R E 2 .5  Technical team training course team may consist of existing government attendees: Sharing and developing expertise information service personnel who will across ministries engage the media at different stages of the project. In some cases, it may be possible to secure the services of either the government or a pri- vate production company to make a short doc- umentary on the project. The project will thus receive coverage in a professional manner, thereby lengthening the “shelf lifeâ€? of public awareness of good slope management prac- tices. 2.4.6 Advocacy task team Political advocacy 2.4.5 Communications task team Elected officials would most likely have been The key responsibilities of the communica- party to the original decisions to undertake the tions task team are as follows: MoSSaiC project; they should be kept informed at all project stages. A policy entrepreneur may • Support the MCU with regard to public emerge as an advocate for MoSSaiC—keeping awareness of the project landslide risk reduction on the political agenda • Produce leaflets, posters, invitations to and helping streamline funding and political community meetings, and other appropri- processes for the initiative. CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   69 F IG U R E 2 . 6  Aspects of communication a. Have a clear and agreed-upon message to b. Consider commissioning a documentary in communicate at the start of a project. which community residents tell the project’s story (source: Government of Saint Lucia). The MCU has a key role to play in develop- A change in government may mean that ing a strategy of engagement with politicians, what was once perceived as innovative policy which could include the following: (such as undertaking MoSSaiC projects) may be less attractive politically. Thus, connecting • Presenting progress documents at cabinet/ the MCU with senior civil servants and techni- government committee meetings cal officers is central to achieving a sustained and sustainable landslide mitigation policy. • Maintaining a one-to-one dialogue with government ministers who have adopted Politicians and the media the vision to reduce landslide risk Politicians may take ownership of the project • Organizing site visits when work is under and promote it—although sometimes this will way, including receiving feedback from be to achieve a political agenda not necessarily community residents in accord with the technical aspects of com- munity prioritization. • Conducting on-site briefings at which com- Combining the media and elected officials pleted works are presented to government can be a very powerful vehicle for project pro- ministers; this can be a powerful tool in motion, especially in the early to mid-stages of a encouraging policy change (figure 2.7). project cycle. The MCU has a key role in brief- ing politicians so that they own the key mes- sages (figure 2.8), and should develop specific F IG U R E 2 .7  On-site briefing plans for coordinated media opportunities. Funding agency advocates It should be assumed that it is a formal require- ment to keep the funding agency appraised of project progress ; this reporting is usually stan- dardized. There is additional benefit in main- taining less formal communications with both current funders and similar agencies to publi- cize project innovation, success in delivering landslide hazard reduction measures on the ground, and lessons learned. Informal visits, 70    C H A P T E R 2 .   P RO J E C T I N C E P T I O N : T E A M S A N D ST E P S 2.5 IDENTIFYING THE FI G U R E 2 .8  Media film elected officials COMMUNITY TASK TEAMS during a MoSSaiC project 2.5.1 Community residents The key responsibilities of community resi- dents with regard to MoSSaiC are as follows: • Discuss and influence project conceptual design—the specific form of community participation and community contracting processes will vary depending on local community structures • Provide detailed local knowledge on past landslides, slope features and processes, possibly with a media component (figure 2.9), rainfall impacts, and drainage issues can help maintain a funding agency’s advocacy • Select representatives from the community of MoSSaiC, especially if funding agency staff to interface with the government task teams turnover is significant. The MCU should create and encourage • Make in-kind contributions to project links with funding agency staff in order to implementation, or earn money as part of a contractors’ team • raise international awareness of a country program, • Learn about good slope management prac- tices and put them in use wherever possi- • potentially provide links to other funding ble. sources, Frequently, the first engagement of com- • provide an opportunity to exchange best munity residents in the project will be infor- practices, and mal as part of initial government task team • build self-esteem among those engaged in site visits to confirm the selection of commu- MoSSaiC at the community level—residents nities for the project. These initial visits are and team members alike would not other- good for opening up discussions with resi- wise gain exposure to such groups or be dents in a nonthreatening way, but formal able to express their perceptions and first- communication with the community should hand project knowledge to them. also occur early on. It is important to identify existing community-based organizations and formal community leadership structures that FI G U R E 2 .9  Funding agency staff on site at initial stage of MoSSaiC project may be required to endorse (or facilitate) a MoSSaiC project. Having established an appropriate means for engaging with the community, a meeting should be held to pres- ent and discuss the proposed project (fig- ure 2.10a). This meeting will often be a multi- purpose event, with media and local government representatives also in atten- dance. These formal and informal occasions give residents the opportunity to express their views and begin to select a group of commu- nity representatives for the project. CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    7 1 Informal opportunities should be created ping, design, and implementation phases so for community residents to contribute to the that local knowledge is captured and acted project on an individual or small-group basis. upon where relevant in the construction Meetings should literally be taken to the com- phase, and the intervention is owned by resi- munity in the form of walk-throughs and dents. Continued community engagement also impromptu discussions. Gathering at a visible provides the best foundation for ongoing drain site in the community encourages others to cleaning and maintenance. join the group out of curiosity as they pass Community representatives (figure  2.10b). In this way, residents effec- • directly interface with government task tively become a task team, contributing their teams as spokespersons for the community; knowledge of slope features and drainage issues. • assist in the mapping of landslide hazard Both informal and formal engagements and drainage issues; allow community members to provide a sig- • collaborate with the community liaison nificant amount of detailed local knowledge team to organize informal and formal com- throughout the project, such as the height the munity meetings (figure 2.10d); flow in a drain might have reached in a partic- ular rainfall event (figure 2.10c). This engage- • collaborate with the engineering task team ment should continue throughout the map- to identify potential contractors and work- F IG U R E 2 .1 0  Aspects of community resident involvement in MoSSaiC a. Meeting with residents at the start of a project b. An informal community focus meeting is often can produce enthusiasm from members of the the best way to begin a project. community to actively participate in the project. c. Residents can help postproject impact assess- d. A formal community meeting is often most ment by indicating maximum observed water levels effective when held after initial informal on-site in completed drains after heavy rainfall. meetings. 7 2    C H A P T E R 2 .   P RO J E C T I N C E P T I O N : T E A M S A N D ST E P S ers from the area, monitor the works, and potentially bidding on the final work packages. report any problems; and A list of contractors from within or near the community should be compiled; they may • communicate and demonstrate good slope have attended a community meeting or have management practices to residents. been recommended. They should be invited to Community-elected leaders can provide participate in the bid process, as part of an useful information when communities are in agreed-upon community contracting process the process of being selected for interventions, (figure 2.11). as well as at the start of a potential project. Such individuals can play a key role in champi- oning the project, given their strong commu- F IGUR E 2 .11  Briefing potential contractors nity engagement and links with government on site after calling for expressions of and agency officials. interest from within the community If appropriate, the community contracting process may involve a selected (and trained) group of community leaders and residents managing the contracting and procurement process with support from the government task teams. Alternatively, if the government handles this process, community leaders and residents should be included as fully as possible. 2.5.2 Construction task team The key responsibilities of the construction task team are as follows: Contractors should be supervised by the • Provide local knowledge as part of the com- engineering and technical task teams during munity mapping process implementation of the works; they may also • Provide insight into local construction have a role in training government technicians practices and designs, and how they could and demonstrating good practices to other potentially be used in the engineering task contractors or communities (figure 2.12). Time team’s design should be invested in community-based con- tractors because of the vital role they play in • Assist in the consideration of transport and vulnerable communities. safe storage of materials, and advise on approximate implementation times 2.5.3 Landowners • Undertake specific works (construction of Building drains and related interventions on drains, installation of household gray water slopes demands that landownership be known and roof water connections) as detailed in to the MCU and that adequate safeguards be contracts put in place to ensure that there will be no dis- putes before, during, or after construction. In • Coordinate with engineering and technical unauthorized housing areas, the following task teams (especially the site supervisor) to landownership possibilities are likely to exist: ensure correct implementation and quality • Single landowner (who possibly resides • Employ workers from within the commu- overseas) who rents out houses, or plots of nity. land for building on, to individual house- holds Locally based contractors can make a vital contribution to the design of works, as well as • Government-owned land CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   73 agency structures. The MCU could, for exam- F IG U R E 2 .1 2  Contractor briefs government ple, be hosted by a ministry through which it technical officers on project implemented in reports. Conversely, in cases where MoSSaiC is his community adopted as a national program, the MCU may report directly to the government. MoSSaiC should not create parallel structures within the government; rather, it should create a manage- ment structure that works with existing roles of accountability wherever possible. Individ- ual MCU members can be delegated to manage the government task team, reflecting their interest and adding value to their existing roles. The government teams should work with the community, within the broad roles defined above, to allow the most marginalized and vul- nerable communities to • have ownership, as they are explicitly engaged in the initial landslide risk map- ping exercise; • provide project guidance, as they are involved in the prioritization of works in their own community; • Multiple landowners with family land par- titioned as families grow and houses are • undertake construction, as contracting built on subdivided land parcels. workers from within the community is an integral part of implementation; The MCU should take particular care to • export the methodology, as community obtain, review, agree on, and implement rele- members provide guidance and support to vant safeguard policies (sections 1.5.3 and 2.3.2). neighboring communities; and • gain self-esteem, as they participate in pro- viding on-site community training to gov- 2.6 INTEGRATION OF MoSSaiC ernment community officials and deliver TEAMS AND PROJECT STEPS presentations at relevant international con- ferences. 2.6.1 Team structure and reporting lines The broad team management structure in Once the task teams have been established, the figure  2.13 highlights the central role of the MCU should prepare a summary document MCU in the management process. listing the selected teams, naming team mem- bers, and assigning broad roles and responsi- 2.6.2 Integrating teams with project bilities; table 2.6 could be used as a template. steps Defining roles and responsibilities is impor- Once all the teams are in place, the MCU can tant in ensuring that project safeguards are create a template that sequences the necessary owned by the relevant task team or the MCU as steps for project implementation. The nine appropriate. It also helps prevent mission drift. components of MoSSaiC (section 1.4.5) can be The MCU should have a reporting line to the used as the basis for the template. government. The exact nature of this reporting Each of the project steps needs to be line will depend on local government and assigned to one or more task team. The par- 74    C H A P T E R 2 .   P RO J E C T I N C E P T I O N : T E A M S A N D ST E P S FI G U R E 2 .1 3  Typical MoSSaiC team reporting structure GOVERNMENT TASK TEAMS COMMUNITY TASK TEAMS Community #1 teams: Mapping team Residents, representatives, construction Community #2 teams: Community liaison team Residents, representatives, construction Community #3 teams: Landslide assessment and Residents, representatives, engineering team MCU construction Government ï?„ Policy maker ï?„ MCU chair ï?„ members ï?„ ï?„ Community #4 teams: Technical support team Residents, representatives, construction Community #5 teams: Communications team Residents, representatives, construction Advocacy team … ticular government and community task team to take responsibility of relevant steps will F IGUR E 2 .14  User group forum activities depend on local conditions. A central role for the MCU is to design, consult on, agree to, and communicate the project steps. The steps shown in table 2.7 (on the following pages) are illustrative of those that have been used in MoSSaiC programs in the Eastern Caribbean; these should be discussed and adapted as local conditions dictate. It is good practice to identify milestones for the project and assimilate them into the agreed-upon project steps. a. A regional workshop captures project outcomes and identifies potential process Table 2.7 integrates summary information improvements. on MoSSaiC teams (sections 2.3 and 2.4), proj- ect steps (section 1.4.5), and milestones. 2.6.3 Establishing a user group community Establishing a user group forum might be use- ful in enabling MoSSaiC to improve slope management practices (achieve behavioral change) as a medium-term outcome. Both local and regional workshops have proved to be a powerful vehicle for senior politicians, b. Community contractors address a workshop contractors, residents, and the media from dif- attended by community residents and other ferent countries to share experiences and stakeholders. develop best practices (figure 2.14). CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   75 TAB L E 2 .7  Summary template of MoSSaiC project teams, steps, and milestones TEAM F M G C ACTIVITY/STEP/MILESTONE CHAPTER  Funding for pilot, project, or phase 2 (carried over or levered from existing projects)     Understand the disaster risk context with respect to landslides; relevance of MoSSaiC approach to local landslide risk context identified     Understand the innovative features and foundations of MoSSaiC 1   Identify general in-house expertise and the appropriate institutional structures for codifying a local approach toward landslide risk reduction    Brief key individuals on MoSSaiC (politicians, relevant ministries, in-house experts)    MILESTONE 1: Key catalytic staff briefed on MoSSaiC methodology    MILESTONE 2: MoSSaiC core unit formed: key responsibilities agreed and defined  Establish the MCU; define and agree on key responsibilities   Identify and establish government task teams; define and agree on key responsibilities 2    Identify and establish community task teams; define and agree on key responsibilities   Agree on a general template for project steps    Gain familiarity with different landslide types and how to identify those that may be addressed by MoSSaiC    Gain familiarity with slope processes and slope stability variables 3   Gain familiarity with methods for analyzing slope stability    MILESTONE 3: Presentation made to MoSSaiC teams on landslide processes and slope stability software   Define the community selection process  Assess landslide hazard  Assess exposure and vulnerability  Assess landslide risk 4   Select communities   Prepare site map information for selected communities    MILESTONE 4: Process for community selection agreed and communities selected    Identify the best form of community participation and mobilization  Include key community members in the project team  Plan and hold a community meeting   Conduct the community-based mapping exercise; this will entail a considerable amount of time in the community   Qualitatively assess the landslide hazard and potential causes 5   Quantitatively assess the landslide hazard and the effectiveness of surface water management to reduce the hazard  Identify possible locations for drains   Sign off on the initial drainage plan: organize a combined MCU-community walk-through and meeting to agree on the initial drainage plan MILESTONE 5: Sign-off on prioritized zones and initial drainage plan (continued) 76    C H A P T E R 2 .   P RO J E C T I N C E P T I O N : T E A M S A N D ST E P S TAB L E 2 .7  Summary template of MoSSaiC project teams, steps, and milestones (continued) TEAM F M G C ACTIVITY/STEP/MILESTONE CHAPTER   Identify the location and alignment of drains  Estimate drain discharge and dimensions   Specify drain construction and design details  Incorporate houses into the drainage plan 6   Produce final drainage plan    Stakeholder agreement on plan    MILESTONE 6: Sign-off on final drainage plan   Prepare work package and request for tender documentation   Conduct the agreed-upon community contracting tendering process   Implement construction 7  Sign off on completed construction    MILESTONE 7: Sign-off on completed construction    Understand how new practices are adopted  Design a communication strategy   Design a capacity-building strategy 8    Plan for postproject maintenance  Map out the complete behavioral change strategy    MILESTONE 8: Communication and capacity-building strategies agreed on and implemented  Agree on key performance indicators (KPIs) for immediate project outputs  Agree on KPIs for medium-term project outcomes 9   Undertake project evaluation MILESTONE 9: Evaluation framework agreed upon and implemented F = funders and policy makers  M = MoSSaiC core unit: government project managers and experts  G = government task teams: experts and practitioners  C = community task teams: residents, leaders, contractors Note: The steps listed for chapters 8 and 9 are relevant throughout the project. CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    7 7 2.7 RESOURCES 2.7.1 Who does what CHAPTER TEAM RESPONSIBILITY ACTIONS AND HELPFUL HINTS SECTION Funders and • Understand MCU missions, roles, and responsibilities 2.2; 2.2.4; policy makers • Identify MCU team members from relevant government 2.3.3; 2.6 ministries and other agencies Establish the MCU Helpful hint: Look for potential members who will command respect and be advocates of MoSSaiC, rather than simply represent particular interests. Coordinate with the MCU MCU Own and communicate the • Understand MCU missions, roles, and responsibilities 2.2 MoSSaiC vision Identify and form government • Identify task team members from relevant government 2.4 task teams ministries and other agencies Once community selected • Initiate community participation process; engage with 2.5 (chapter 4), identify community community residents and representatives task team members • Review MoSSaiC components with respect to task team 2.2.4; 2.6 capacity and resources • Modify project step template Establish project step template Helpful hint: This is a vital step in the process of project inception. Organize a meeting to review the template and encourage the modification of the template to fit local conditions and protocols. Coordinate with new task teams Government task Provide the MCU with assess- • Become familiar with MoSSaiC approach and local context 2.2; 2.2.4 teams ment of task team capacity for • Identify specific team skills and resources for project each project step delivery Coordinate with the MCU Community task • Become familiar with MoSSaiC approach with respect to 2.5 Once community selected teams community context (chapter 4), coordinate with relevant government task teams • Advise on existing community-based leadership and the MCU to identify structures and organizations appropriate form of community • Identify specific community-based skills and resources participation • Attend community meetings Coordinate with government task teams 78    C H A P T E R 2 .   P RO J E C T I N C E P T I O N : T E A M S A N D ST E P S 2.7.2 Chapter checklist SIGN- CHAPTER CHECK THAT: TEAM PERSON OFF SECTION 99List compiled of individuals supportive of MoSSaiC across government/agencies 2.3.3 99Milestone 2: MCU formed 99MCU has identified individuals for government task teams 2.4 99MCU and appropriate government task teams have identified individuals for 2.5 community task teams 99MCU has established clear line of responsibility to a specific government entity 2.6 99All necessary safeguards complied with 1.5.3; 2.3.2 2.7.3 References Magazine 19 (3). http://practicalaction.org/ Anderson, M. G., and E. A. Holcombe. 2004. practicalanswers/product_info.php?products_ “Management of Slope Stability in id=214. Communities.â€? Insight 1: 15–17. Ostrom, E., C. Gibson, S. Shivakumar, and —. 2006a. “Purpose Driven Public Sector Reform: K. Andersson. 2001. “Aid, Incentives, and The Need for within-Government Capacity Build Sustainability: An Institutional Analysis of for the Management of Slope Stability in Development Cooperation.â€? Sida Studies in Communities (MoSSaiC) in the Caribbean.â€? Evaluation Report 02/01, Stockholm. Environmental Management 37: 5–29. Prater, C. S., and M. K. Londell. 2000. “Politics of —. 2006b. “Sustainable Landslide Risk Natural Hazards.â€? Natural Hazards Review 1 (2): Reduction in Poorer Countries.â€? Proceedings of 73–82. the Institution of Civil Engineers—Engineering Raschky, P. A., and M. Schwindt. 2009. “Aid, Sustainability 159: 23–30. Natural Disasters and the Samaritan’s Anderson, M. G., E. A. Holcombe, and D. Williams. Dilemma.â€? Policy Research Working Paper 2007. “Reducing Landslide Risk in Poor Housing 4952, World Bank, Washington, DC. Areas of the Caribbean—Developing a New Roberts, N. C., and P. J. King. 1991. “Policy Government-Community Partnership Model. Entrepreneurs: Their Activity Structure and Journal of International Development 19: 205–21. Function in the Policy Process.â€? Journal of Buchanan, J. M. 1977. “The Samaritans’ Dilemma.â€? Public Administration Research and Theory 1 (2): In Freedom in Constitutional Contract, ed. J. M. 147–75. Buchanan. College Station, TX: Texas A & M University Press. UNDP (United Nations Development Programme). 2006. “A Review of Selected Capacity IEG (Independent Evaluation Group). 2000. “IEG Assessment Methodologies.â€? http://lencd.com/ Report on Project ID P003985 Indonesia.â€? data/docs/242-A%20Review%20of%20 World Bank, Washington, DC. Selected%20Capacity%20Assessment%20 —. 2005. Putting Social Development to Work Methodologies.pdf. for the Poor: An OED Review of World Bank Venture Philanthropy Partners. 2001. Effective Activities. Washington, DC: World Bank. Capacity Building in Nonprofit Organizations. Mansuri, G., and V. Rao. 2003. Evaluating http://www.vppartners.org/sites/default/files/ Community-Based and Community-Driven reports/full_rpt.pdf. Development: A Critical Review of the Evidence. —. 2003. Strategic Communication for Development Research Group. Washington, Development Projects: A Toolkit for Task Team DC: World Bank. Leaders. http://siteresources.worldbank.org/ Maskrey, A. 1992. “Defining the Community’s Role EXTDEVCOMMENG/Resources/ in Disaster Mitigation.â€? Appropriate Technology toolkitwebjan2004.pdf. CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   79 “A failure to address the underlying risk drivers will result in dramatic increases in disaster risk and associated poverty outcomes. In contrast, if addressing these drivers is given priority, risk can be reduced…â€? —United Nations, “Global Assessment Report on Disaster Risk Reductionâ€? (2009, 4) CHAPTER 3 Understanding Landslide Hazard 3.1 KEY CHAPTER ELEMENTS 3.1.1 Coverage This chapter identifies the physical and human Slope Stability in Communities) foundations. drivers for landslide hazard. Understanding The listed groups should read the indicated the scientific basis for assessing landslide haz- chapter sections. ard is one of the MoSSaiC (Management of AUDIENCE CHAPTER F M G C LEARNING SECTION    How to identify types of landslides that can be addressed by MoSSaiC 3.3   Slope stability factors and common landslide hazard assessment methods 3.4    Detailed localized factors that affect slope stability in communities 3.5   Specific scientific landslide hazard assessment methods relevant to MoSSaiC 3.6 F = funders and policy makers  M = MoSSaiC core unit: government project managers and experts  G = government task teams: experts and practitioners  C = community task teams: residents, leaders, contractors 3.1.2 Documents CHAPTER DOCUMENT TO BE PRODUCED SECTION Briefing by landslide assessment and engineering task team for the MoSSaiC core unit and all 3.2–3.5 other task teams on (1) MoSSaiC applicability to local landslide types; (2) landslide preparatory, aggravating, and triggering factors; and (3) the scientific basis for assessing slope stability, especially with respect to locally available expertise and software 81 3.1.3 Steps and outputs STEP OUTPUT 1. Gain familiarity with different landslide types and how to identify MoSSaiC core unit (MCU) and those that may be addressed by MoSSaiC task teams understand the • Review landslide process introductory material in this book and types of landslide risk for other sources which MoSSaiC is applicable 2. Gain familiarity with slope processes and slope stability variables MCU and task teams can • Review landslide process variables as introduced in this book identify different levels of landslide hazard and underlying physical causes 3. Gain familiarity with methods for analyzing slope stability MCU and task teams can • Review slope stability software as introduced in this book and provide scientific rationale for other sources landslide mitigation measures Those on the MoSSaiC landslide assessment there are few examples of effective physical and engineering task team with the most expe- landslide hazard reduction measures in such rience in analysis of landslide risk could use communities (Wamsler 2007). the material in this chapter to organize a pre- Development agencies have mainstreamed sentation to the MoSSaiC core unit (MCU) and disaster risk management policies, estimating other task teams to foster a common and that for every dollar spent in mitigation, two to shared understanding of landslide triggering four dollars will be saved in avoided costs processes, the relevance of MoSSaiC (chap- (Mechler 2005). Landslide risk mitigation ter 1), and the associated project structure and requires an understanding of the interactions implementation steps (chapter 2). between physical and human risk drivers, and how to assess the risk and deliver solutions at a 3.1.4 Community-based aspects scale that relates to these risk drivers. Com- The chapter outlines the need to understand munity-scale landslide hazard reduction can landslide triggering mechanisms at the house- only be successful if landslide hazard mecha- hold/local scale within communities. nisms and triggers are understood. Such an understanding 3.2 GETTING STARTED • ensures that any landslide risk assessment is scientifically informed, 3.2.1 Briefing note • ensures that any proposed landslide risk Importance of understanding landslide management strategies are appropriate to processes the specific local landslide hazards, Both the occurrence and the impact of land- • determines if a MoSSaiC-style drainage slides are increasing, especially in tropical intervention will address the landslide haz- developing countries (Charveriat 2000; UNDP ard, 2004), with the majority of landslide fatalities • increases the ability of those implementing occurring in urban areas (Petley 2009; UN the project to justify the risk reduction 2006). Here, intense rainfall triggers land- measures adopted, slides in highly weathered soils and rapid urbanization increases the susceptibility of • helps build confidence within the commu- slopes to failure, while socioeconomic vulner- nity that the fundamental causes of risk are ability increases the damage caused. Even so, being tackled, and 82    C H A P T E R 3 .   U N D E R S TA N D I N G L A N D S L I D E H A Z A R D • encourages a holistic and strategic approach grams focus on assessing vulnerability and to implementation of landslide risk reduc- exposure to landslide hazards; relatively few tion measures among all stakeholders. look at the physical causes of the hazard at the highly localized scales at which they occur. Landslide hazard as a component of landslide Various natural and human preparatory and risk aggravating factors can reduce slope stability Three components contribute to landslide and trigger landslides. By understanding these risk: the physical landslide hazard (its likeli- driving factors and identifying the dominant hood, location, and magnitude), the exposure landslide mechanisms, it is often possible to of different elements (such as people, build- address the root causes of landslides and thus ings, public utilities, economic infrastructure, reduce the hazard (the frequency or magni- or the environment) to that hazard, and the tude of the event). vulnerability of those elements to damage by One of the main premises of MoSSaiC is the hazard. that rainfall-triggered landslide hazards can often be reduced in vulnerable communities in • Landslide hazard is defined in terms of its developing countries. This is because a com- frequency (e.g., an annual probability of 0.1, mon driver for such landslide hazards is poor meaning a 1-in-10-year landslide event), slope drainage and surface water infiltration magnitude, and type at a particular location into weathered slope materials on densely or within a wider region. When the likeli- populated urban slopes. Scientific principles hood of a particular landslide hazard is and methods can be used to confirm the role of expressed in relative or qualitative terms surface water infiltration and therefore indi- rather than as a probability, it is more cate a potential solution—the construction of appropriate to refer to susceptibility (more appropriately located surface water drains. versus less susceptible to landslides). Science as part of the landslide risk • The exposure of people, structures, ser- management process vices, or the environment to a specific land- slide hazard is determined by the spatial A typical disaster risk management process and temporal location of those elements was introduced in section 1.3.2. Table 3.1 pres- with respect to the landslide. ents the scientific basis of each step in this pro- cess with particular reference to landslide risk • Vulnerability is an expression of the poten- management and the MoSSaiC approach. tial of the exposed elements to suffer harm or loss. Thus, exposure and vulnerability 3.2.2 Guiding principles relate to the consequences or results of the The following guiding principles apply in landslide, and not to the landslide process understanding landslide hazard: itself (Crozier and Glade 2005). In many cases, exposure is treated as an implicit part • Develop a shared understanding of land- of vulnerability assessment. Vulnerability is slide processes within the MCU related to the capacity to anticipate a land- • Identify and collate data on past, existing, slide hazard, cope with it, resist it, and or predicted landslide hazards in the proj- recover from its impact. A combination of ect area and on physical and human factors physical, environmental, social, economic, relating to slope stability political, cultural, and institutional factors determine vulnerability (Benson and Twigg • Explain and explore the scientific ratio- 2007). nale for landslide hazard reduction in a To understand landslide risk, it is necessary way that is accessible to residents in vul- to understand the nature and causes of the nerable communities; assure residents hazard. Many development studies and pro- that the local landslide processes are CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    8 3 TAB L E 3 .1  Typical landslide risk management project steps and associated scientific basis for MoSSaiC STEP MoSSaiC SCIENCE BASE Landslide Identify and Confirm the relevance of MoSSaiC. A basic understanding of landslide types and triggers is risk formulate the needed in order to identify the dominant landslide hazard in the project area. MoSSaiC management project specifically addresses rainfall-triggered rotational/translational landslides in weathered project materials. preparation Identify the Identify communities most at risk from landslides. This requires assessment of the relative broad landslide rotational/translational landslide susceptibility or hazard in different areas. This hazard risk information is combined with an assessment of community exposure and vulnerability. Landslide Understand and Identify the underlying landslide hazard drivers and confirm the level of the hazard. For risk estimate the selected communities, the local slope features and slope stability processes must be identified, assessment specific science-based methods used to confirm the hazard drivers, and the vulnerability of exposed landslide risk households assessed. Evaluate the risk Compare the landslide risk with other risks. Expert judgment and/or scientific methods should be applied to determine where investment in landslide risk reduction is a priority. Identify disaster Determine whether the landslide hazard can be reduced. Disaster risk reduction options risk reduction include avoiding or reducing the hazard, reducing vulnerability, or transferring the risk. MoSSaiC options focuses on landslide hazard reduction through appropriate surface water management measures. For each community, expert judgment and/or scientific methods should be applied to confirm whether this MoSSaiC approach will be effective. Plan the risk Design the landslide hazard reduction measures. Engineers should design the physical Landslide mitigation measures to directly address the localized landslide hazard drivers. In the case of MoSSaiC, this risk requires appropriate alignment and design of a drainage network to capture surface water and reduction reduce infiltration. Implement risk Construct landslide hazard reduction measures. This involves issuing contracts for and mitigation managing construction, and raising public awareness. Knowledge of slope processes and construction of drainage works are vital in ensuring that hazard reduction measures are correctly implemented. Monitor and Assess project progress, sustainability, and impact. Science-based methods should be used to evaluate determine the effectiveness of landslide hazard reduction measures. understood and that the project is likely to • Their inherent limitation in predicting spe- be effective in addressing the causes of the cific landslide locations, timing, and causes problem due to the mismatch between coarse map scales and fine-scale variations in slope 3.2.3 Risks and challenges processes (Keefer and Larsen 2007) Regional policies and local landslide hazards • Their lack of utility in land-use planning for In international development, disaster risk exposure reduction (Opadeyi, Ali, and Chin reduction funding policies are often decided 2005), as high-density unauthorized hous- at a regional level and then translated into ing often already occupies hazardous national programs to address multiple risk slopes. types. This top-down approach typically Holistic awareness of slope processes leads to the production of wide-area qualita- tive maps of landslide susceptibility that Several interrelated factors can affect the sta- practitioners in developing countries may bility of a slope at a variety of spatial and tem- find difficult to apply (Zaitchik and van Es poral scales. These factors should be investi- 2003). There are two possible reasons for the gated at the relevant scale using either a lack of uptake of such maps (Holcombe and qualitative or quantitative (modeling) Anderson 2010): approach or a mixture of both. Direct mea- 8 4    C H A P T E R 3 .   U N D E R S TA N D I N G L A N D S L I D E H A Z A R D surement of all slope parameters is not always ect in terms of funding constraints, geographi- possible; however, engineers or scientists will cal extent, policy context, and type of landslide be able to make an expert judgment of the hazard to be mitigated. dominant causes of the landslide hazard based Correctly identifying the type of landslide on their knowledge of the principles govern- hazard affecting a particular area is vital. Dif- ing slope stability. ferent landslide types have very different physical mechanisms and consequences. Each 3.2.4 Adapting the chapter blueprint to type therefore requires a different hazard existing capacity assessment approach and set of mitigation This chapter provides an introduction to land- measures. This section presents a simple clas- slide processes and the various factors that can sification of landslide types and identifies affect slope stability. It identifies the main those that may be mitigated by a MoSSaiC forms of landslide hazard assessment appro- project—namely, rotational and translational priate at different spatial scales and for various rainfall-triggered slides in weathered slope levels of data and expertise. materials affecting multiple households or Members of the MCU and task teams entire urban communities. should understand basic slope stability pro- MCU and task teams should use this sec- cesses in order to configure the landslide haz- tion to identify the dominant landslide haz- ard reduction measures appropriately and ards in the project area in terms of share this knowledge with community resi- dents and other stakeholders. The MCU and • types of movement and material involved, government task teams should have at least • geometry, one civil, environmental, or geotechnical engi- • triggering mechanism, and neer, or an expert in physical, geotechnical, or • slope stability over time. hydrological sciences, who can lead the land- slide hazard assessment process. The project 3.3.1 Types of slope movement and should be scientifically justified and that justi- landslide material fication understood by all involved. Although many types of mass movements are The MCU should begin by assessing avail- referred to as landslides, the technical use of able capacity in this area. Use the matrix on the term applies only to mass movements the next page to help make that assessment. where there is a distinct zone of weakness that 1. Assign a capacity score from 1 to 3 (low to separates the slide material from more stable high) to reflect existing capacity for each underlying material. For a helpful, well-illus- element in the matrix’s left-hand column. trated guide to different landslide types and geometries, see USGS (2004). 2. Identify the most common capacity score as Varnes (1978) classified five principle types an indicator of the overall capacity level. of mass movement in three types of slope 3. Adapt the blueprint in this chapter in accor- material (table 3.2). As highlighted in the table, dance with the overall capacity level (see MoSSaiC is designed to address rotational and guide on the bottom of next page). translational slides in predominately weath- ered materials (unconsolidated fine soils) that are principally triggered by rainfall. 3.3 LANDSLIDE TYPES AND • Rotational slide. The surface of rupture is THOSE ADDRESSED BY curved concavely upward, and slide move- MOSSAIC ment is roughly rotational (figure 3.1a). The first step in the landslide risk manage- • Translational slide. The landslide mass ment process is to define the scope of the proj- moves along a roughly planar surface with CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    8 5 EXISTING CAPACITY CAPACITY ELEMENT 1 = LOW 2 = MODERATE 3 = HIGH MCU member(s) familiar with No major education in Some MCU members have a Two or more MCU members landslide processes and hazard landslide processes or basic grounding in landslide have sound education in reduction measures previous experience with processes or some experience landslide processes and landslide hazard reduction with landslide hazard experience in implementing projects reduction projects landslide hazard reduction projects Training available on landslide No local provision for training Courses on some aspects of Training courses on both processes and hazard landslide processes and hazard landslide processes and hazard reduction reduction locally available reduction locally available Availability of slope stability No slope stability analysis Either slope stability analysis Slope stability analysis analysis software and software or expertise available software or expertise available software and expertise expertise to government, but not both available within government and used on projects Government capacity to Limited government capacity One-off landslide mitigation Government department support landslide mitigation to support and implement projects previously under- routinely handles landslide (hazard reduction) projects landslide mitigation projects taken by government mitigation work Project safeguards Documented safeguards need Documents exist for some Documented safeguards to be located; no previous safeguards available from all relevant experience in interpreting and agencies operating safeguard policies CAPACITY LEVEL HOW TO ADAPT THE BLUEPRINT 1: Use this chapter The MCU needs to strengthen its capacity in understanding landslide processes and using relevant in depth and as a analytical software. This might involve the following: catalyst to secure • Working with local commercial or higher education partners to share and learn from their experience in support from other slope stability analysis agencies as appropriate • Searching for colleagues in government with relevant slope stability experience and considering their appointment to the MCU • Approaching suitable materials laboratories and consultants for data on soil material properties 2: Some elements The MCU has strength in some areas, but not all. Elements that are perceived to be Level 1 need to be of this chapter will addressed as above. Elements that are Level 2 will need to be strengthened, such as the following: reflect current • Where there is no slope stability analysis software, seek training on the use and application of such practice; read the software remaining elements in depth and use • Where there is limited existing government coordination of landslide hazard assessment, pool the them to further relevant expertise and data from different ministries and agencies strengthen capacity • Where there is limited or incomplete understanding of landslide causes, provide a technical briefing session for nonexperts based on material in this chapter 3: Use this chapter The MCU is likely to be able to proceed using existing proven capacity. The following would nonetheless as a checklist be good practice: • Document relevant prior experience in landslide hazard assessment and related safeguard documents • Endorse such a document at an MCU meeting prior to commencement of works 8 6    C H A P T E R 3 .   U N D E R S TA N D I N G L A N D S L I D E H A Z A R D TAB L E 3 .2  Slope instability classification TYPE OF MATERIAL UNCONSOLIDATED SOIL TYPE OF MOVEMENT BEDROCK Coarse Fine Falls Rock fall Debris fall Earth fall Topples Rock topple Debris topple Earth topple Rotational Rock slide Debris slide Earth slide—the landslide type Slides relevant to MoSSaiC Translational Flows Rock flow Debris flow Earth flow Complex Combination of two or more types Source: Cruden and Varnes 1996. © National Academy of Sciences, Washington, DC, 1996. Reproduced with permission of the Transportation Research Board. Note: The types of slope movement and associated material that are addressed by MoSSaiC are highlighted. little rotation or backward tilting (fig- fied and plotted (in accordance with fig- ure  3.1b). A block slide is a translational ure 3.2). slide in which the moving mass consists of a The scale of landslides in vulnerable com- single unit or a few closely related units that munities in the tropics will generally be deter- move downslope as a relatively coherent mined by soil depth, since the slip surface is mass. often at the interface between the soil and the 3.3.2 Landslide geometry and features bedrock (or at a marked change of soil weath- ering grade). Typical depths to the slip surface Different types of landslide can be recognized may be in the range 1–10 m. by their geometry and features (figure  3.2). The lateral extent of landslides in such The idealized forms shown in figures 3.1 and locations is often controlled by topographic 3.2 are not always easy to identify in the field if features such as zones of drainage conver- vegetation cover obscures the landslide or if gence and deeper soils. Where more localized the landslide is old. Only comparatively recent factors are acting to destabilize the slope, the landslides are likely to exhibit an identifiable landslide may be less extensive. Typical maxi- failure zone at the head of the moved mass. mum widths of the main body of the landslides When mapping landslide locations, as many (figure 3.2, feature 6) may be in the range of these features as possible should be identi- 10–50 m or more. Rotational landslides in soils are not as mobile as some other forms of landslide (such FI G U R E 3 .1  Characteristics of rotational as debris slides). Typically, the surface of sepa- and translational slides in predominantly ration of rotational landslides (figure 3.2, fea- weathered materials ture 12) may be in the range of a few meters to a. Rotational slide b. Translational slide about 100 m, depending on the volume of material involved and the slope angle. 3.3.3 Landslide triggering events: Rainfall and earthquakes Every slope has stabilizing and destabilizing forces. The different preparatory and aggra- vating factors that determine the relative sus- Source: USGS 2004; reproduced with permission. ceptibility of a slope to landslides are detailed in section 3.4. A slope that is relatively suscep- CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    8 7 FI G U R E 3 .2  Definitional features of a landslide 1. Crown: The undisplaced material adjacent to the highest parts of the main scarp. 2. Main scarp: A steep surface on the undisturbed ground at the upper edge of the 14 landslide, caused by movement of the displaced material away from the undisturbed A ground; the visible part of the surface of rupture. 16 5 3. Top: The highest point of contact between the displaced material and the main scarp. 20 4. Head: The upper parts of the landslide along the contact between the displaced 15 material and the main scarp. 5. Minor scarp: A steep surface on the displaced material of the landslide produced by 18 differential movements in the displaced material. 10 B 6. Main body: The part of the displaced material of the landslide that overlies the surface 12 of rupture between the main scarp and the toe of the surface of rupture. 7. Foot: The portion of the landslide that has moved beyond the toe of the surface of rupture and overlies the original ground surface. 19 8. Tip: The point of the toe farthest from the top of the landslide. 1 9. Toe: The lower, usually curved, margin of the displaced material of a landslide; it is the most distant from the main scarp. 10. Surface of rupture: The surface that forms the lower boundary of the displaced A 3 4 6 11 7 8 B material below the original ground surface. 11. Toe of the surface of rupture: The intersection (usually buried) between the lower 9 part of the surface of rupture of a landslide and the original ground surface. 2 12. Surface of separation: The part of the original ground surface overlaid by the foot of the landslide. 19 13. Displaced material: Material displaced from its original position on the slope by move- original ground level ment in the landslide. It forms both the depleted mass and the accumulation. extent of displaced material 14. Zone of depletion: The area of the landslide within which the displaced material lies below the original ground surface. undisturbed ground 15. Zone of accumulation: The area of the landslide within which the displaced material lies above the original ground surface. 16. Depletion: The volume bounded by the main scarp, the depleted mass, and the original ground surface. 17. Depleted mass: The volume of the displaced material that overlies the rupture surface but underlies the original ground surface. 18. Accumulation: The volume of the displaced material that lies above the original ground surface. 19. Flank: The undisplaced material adjacent to the sides of the rupture surface. Compass directions are preferable in describing the flanks but if left and right are used, they refer to the flanks as viewed from the crown. 20. Original ground surface: The surface of the slope that existed before the landslide took place. Source: International Geotechnical Societies UNESCO Working Party on World Landslide Inventory 1993. tible to landslides may exist in a state of mar- Lumb 1975). MoSSaiC is specifically targeted ginal stability for a long period until a particu- to address this form of landslide hazard lar event decreases the stabilizing forces and/ through the construction of a network of sur- or increases the destabilizing forces, triggering face water drains. a landslide. The most common landslide trig- Rainfall, slope hydrology, and landslides gers are rainfall events and seismic events (earthquakes). Because these triggers act on a Rainfall-triggered landslides occur in most slope in different ways, it is important to dis- mountainous landscapes and can have an tinguish between those landslides that are enormous effect on the landscape, properties, rainfall triggered versus those that are seismi- and people. Intense or prolonged rainfall cally triggered so that appropriate risk mitiga- infiltrates the slope surface, causing an tion measures can be identified. increase in soil pore water pressure and an The majority of landslides in the humid associated lowering of slope material tropics are triggered by rainfall (Crosta 2004; strength. The forces that act to stabilize the 8 8    C H A P T E R 3 .   U N D E R S TA N D I N G L A N D S L I D E H A Z A R D slope are thus reduced, and the slope fails along the zone where the destabilizing forces F IGUR E 3 . 3  Typical surface and subsurface water sources and flow paths associated with unauthorized construction on hillslopes (gravity and loading) overcome the stabiliz- ing forces. rainfall Urban development can alter the prepara- tory factors affecting slope stability, changing surface water slope geometry, loading, surface cover, and runo and inï¬?ltration slope hydrology. Significantly, urban develop- water from roofs ment can increase the effectiveness of rainfall with no guttering or drain connection in triggering landslides by changing natural drainage routes, concentrating surface water flows, changing surface vegetation cover (which would normally intercept and store groundwater rainfall and remove water from the soil), badly drained broken, blocked, roads and paths increasing rainfall runoff from impermeable or unlined drains surfaces, and increasing surface water infiltra- piped water from households tion in other areas (figure 3.3). The most vul- and septic tanks/pit latrines nerable communities in developing countries will probably not have sufficient surface water drainage, but may have publicly supplied piped Seismic events water, which further increases the amount of water on the slope. Rainfall-triggered land- Seismic activity can also affect the forces act- slide hazard is thus often increased by urban- ing on a slope and trigger landslides. Cur- ization. rently, MoSSaiC does not address the land- As noted, in humid tropical developing slide mechanisms associated with this countries, the majority of fatalities and physi- triggering process. Nevertheless, the MCU cal losses occur in urban areas (Petley 2009). should have some familiarity with seismic At the local scale, even small landslide events risk where it coexists with the potential for in densely populated areas can result in sig- rainfall-triggered landslides. In such cases, a nificant loss of life and property and stall eco- holistic approach to disaster risk reduction nomic development. Houses may be lost or should be taken if possible. For example, the made unsafe, and community infrastructure MoSSaiC approach to community-scale slope destroyed (figures 3.4a and b). Multiple land- drainage networks, plus the house-by-house slides may be widespread throughout the area installation of roof guttering and gray water (figure 3.4c). connections to the drains, could be coupled Shallow and deep-seated landslides alike with guidelines on earthquake-resilient prop- can be triggered by rainfall. Records of land- erty design for such communities (Build slides and associated rainfall triggers (charac- Change 2011). terized by intensity, duration, and frequency) Globally, many locations have oversteep- can be used to predict the timing of future ened and highly weathered hillsides, where rainfall-triggered landslide events. Extensive large landslides could cause significant harm research has been conducted to identify both to local communities—many of which are landslide-prone terrains (Hansen 1984; already vulnerable in terms of housing struc- Soeters and van Westen 1996) and the rainfall tures and poverty. The 2001 earthquakes in El intensities and durations that cause slopes to Salvador (figure 3.5) are a notable example in fail (Larsen and Simon 1993). These two issues this regard, causing over 600 landslides and are discussed further in section 3.4; De Vita et resulting in many hundreds of fatalities, with al. (1997) provide an extensive bibliography on 585 deaths in the community of Las Colinas rainfall-triggered landslides. alone (figure 3.6). CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    8 9 Empirical evidence linking seismic activ- FI G U R E 3 .4  Rotational and translational landslides ity; preparatory factors such as slope angle, geology, and soils; and landslide events can be formalized by measures of seismic intensity. An instrument-based measure of seismic intensity developed by Arias (1970) was first used for analyzing the occurrence of land- slides by Wilson and Keefer (1985), and its use has become relatively widespread for that purpose since. The Arias intensity, for any given strong-motion recording, is expressed as Ia = Ï€/2g ∫0Td [a(t)2]dt Where: a. Rotational slide in St. Lucia triggered by rainfall during Hurricane Dean Ia = Arias intensity in units of velocity (2007) caused the loss of three houses. t = time a(t) = ground acceleration as a function of time Td = total duration of the strong-motion record g = acceleration due to gravity Arias intensity is a ground motion parame- ter that captures the potential destructiveness of an earthquake as the integral of the square of the acceleration-time history. It correlates well with several commonly used demand measures of structural performance, liquefac- tion, and seismic slope stability (Travasarou, Bray, and Abrahamson 2003). Based on theo- retical considerations, statistical analysis of strong-motion attenuation, and empirical data b. Translational slide in St. Lucia triggered by ~500 mm of rainfall in 24 on landslide limits in historical earthquakes, hours associated with Hurricane Tomas (2010); slide caused the loss of a the Arias intensity thresholds can be related to road (center) and significantly damaged houses at the landslide crest. types of landslide (table 3.3) (Keefer 2002; Keefer and Wilson 1989; Wilson and Keefer 1985). Keefer (2002, 504) notes that while earth- quake-induced landslides have been docu- mented for more than 3,700 years, it is clear that more seismic data are needed: …the number of earthquakes with relatively complete data on landslide occurrence is still small, and one of the most pressing research needs is for complete landslide inventories for many more events in a wider variety of environments. c. Hillside-wide translational landslides St. Lucia triggered by Hurricane Tomas. These empirical data, when coupled with analytical tools such as geographic informa- 9 0    C H A P T E R 3 .   U N D E R S TA N D I N G L A N D S L I D E H A Z A R D FI G U R E 3 .5  Distribution of seismicity during the 2001 El Salvador earthquakes 14°0'N ï‚«earthquake depth (m) 13°0'N ï‚Ÿ 0–20 ï?¬ 21–50 ï?¬ > 50 90°0’W 89°0’W 88°0’W Source: Garcia-Rodriguez et al. 2008. Note: Data were recorded and relocated by the Salvadoran Short-Period Network of the Center for Geotechnical Investigations. Shown are the main earthquakes on January 13, February 13, and February 17, 2001, and their aftershocks. The January 13 earthquake, which triggered over 600 landslides including in Las Colinas, was located in the subduction zone between the Cocos and Caribbean plates, with a magnitude of 7.7 (moment magnitude) and a focal depth of 40 km. FI G U R E 3 .6  Aerial view of earthquake- TAB LE 3 . 3  Arias intensity and associated landslide categories triggered landslide in Las Colinas, El Salvador, ARIAS INTENSITY VALUE RESULTANT LANDSLIDE January 13, 2001 THRESHOLD CATEGORY 0.11 ms−1 Disrupted landslides 0.32 ms−1 Coherent slides, lateral spreads, and flows 0.54 ms−1 Lateral spreads and flows Source: Keefer and Wilson 1989. shows the landslide velocity scale proposed by Cruden and Varnes (1996). Source: Garcia-Rodriguez et al. 2008. In the tropics, rainfall-triggered landslide movement typically lasts anywhere from a few minutes to a few hours. Progressive slides and tion systems (GIS), could lead to substantial subsequent slope settlement can continue additional refinements in physically based over periods as long as a year or more. Fig- models that relate seismic shaking and geo- ure  3.7 shows a rotational landslide periodi- logic conditions to slope failure. cally moving over five years, causing increased damage to the property. 3.3.4 Slope stability over time The magnitude of a landslide will deter- Landslide velocities can vary significantly mine the damage caused to people and prop- depending on type, material, trigger, and a erty. Landslide magnitude is defined by the range of other slope properties. Table 3.4 velocity of the slide and the size of the area CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    9 1 TAB L E 3 .4  Landslide velocity scale VELOCITY VELOCITY TYPICAL CLASS DESCRIPTION (mm/s) VELOCITY PROBABLE DESTRUCTIVE SIGNIFICANCE Catastrophe of major violence; buildings destroyed by impact of 7 Extremely rapid displaced material; many deaths; escape unlikely 5 × 103 5 m/s 6 Very rapid Some lives lost; velocity too great to permit all persons to escape 5 × 10 1 3 m/min Escape evacuation possible; structures, possessions, and equipment 5 Rapid destroyed 5 × 101 1.8 m/h Some temporary and insensitive structures can be temporarily 4 Moderate maintained 5 × 103 13 m/month Remedial construction can be undertaken during movement; insensi- 3 Slow tive structures can be maintained with frequent maintenance work if total movement is not large during a particular acceleration phase 5 × 105 1.6 m/year 2 Very slow Some permanent structures undamaged by movement 5 × 10 7 15 mm/year Imperceptible without instruments; construction possible with Extremely slow precautions Source: Cruden and Varnes 1996. © National Academy of Sciences, Washington, DC, 1996. Reproduced with permission of the Transportation Research Board. FI G U R E 3 .7  Progressive landslide a. In 2005, rainfall triggered a progressive b. The same house in 2008 shows the c. The same house in 2010 shows the rotational landslide in a vulnerable slow progressive movement of the structure’s near collapse after five years community in St. Lucia. rotational failure. of very slow progressive slope failure. affected, in terms of both the actual failed area (reduction in hazard) or a decrease in stability and the travel distance of the displaced mate- due to the slide’s creating an unstable scarp rial (the accumulation zone). (figure 3.8). The slope’s postfailure stability can also In an area of existing landslides, postfailure contribute to overall landslide impact. stability should be carefully assessed to iden- Depending on the geometry of the slide and tify possible future hazard, since this may be the resulting geometry of the slope, there may either increased or decreased by occurrence of be either a relative increase in overall stability a slope failure. 92    C H A P T E R 3 .   U N D E R S TA N D I N G L A N D S L I D E H A Z A R D • Section 3.5 describes how each of the slope FI G U R E 3 .8  Postfailure slope stability stability variables can be identified, mea- sured, and interpreted in the field. • Section 3.6 details the physically based slope stability assessment methods that are particularly relevant to MoSSaiC. 3.4.1 Landslide preparatory factors and triggering mechanisms The factors that determine the stability of a slope can be categorized as a. Landslide caused by soil water convergence at, and immediately above, the zone of failure, • preparatory factors, determining the sta- the impact of which serves to reduce subse- bility of a slope over a period of time, quent landslide risk since the local slope angle has been reduced as a consequence of the • triggering mechanisms, the dynamic events failure. that result in a landslide, and • aggravating factors, the many human activities that can reduce the stability of a slope without necessarily triggering a land- slide (table 3.5). These various factors will act and interact across a particular slope to determine its sta- bility state at any point in time. Each factor must be taken into account and their com- bined influence assessed in order to under- stand the stability of a slope. Factors that cause landslides are often quite localized in nature. Extensive work in Hong Kong SAR, China, has demonstrated that, for a large number of landslides, the main rainfall trigger works in conjunction with highly specific local preparatory factors (GCO b. Landslide below unauthorized houses triggered by the discharge of upslope water, 1984). Table 3.6 provides a summary of the causing oversteepening at the crest of the range of scales over which the different pre- landslide, and subsequent increase in landslide paratory and triggering factors could be hazard. expected to operate. To deliver landslide haz- ard reduction measures at the community scale (the MoSSaiC objective), the relevant 3.4 SLOPE STABILITY PROCESSES slope processes must be assessed at the 1–100 AND THEIR ASSESSMENT m scale. This section introduces the different factors 3.4.2 Overview of slope stability and variables that can determine the stability assessment methods of a slope and some of the main methods for In discussing the methods and outputs of an assessing slope stability. More information on assessment of slope stability, it is necessary to slope stability processes and assessment is understand the difference between landslide provided in the following two sections: susceptibility and landslide hazard: CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   93 TAB L E 3 .5  Factors determining slope stability and associated assessment methods FACTOR DETERMINING SLOPE STABILITY Preparatory Aggravating ASSESSMENT METHOD Slope angle Construction—oversteepening of slopes GIS, maps, survey, Abney level Slope hydrology Poor or altered slope drainage—leaking • Topographic convergence from maps/ or incomplete drains; blocked drains and survey natural channels; saturated soils; water • Water table from piezometer records from house roofs, kitchens, and bathrooms • Detailed on-site drainage survey Slope material depth, structure, and type Poorly compacted fill or previously failed Material grades, shear box direct material measurement Vegetation Change or removal of vegetation due to Field observation cultivation or construction Loading Overloading—dense, unplanned housing, Survey of housing density and construc- water tanks, or infrastructure tion material Previous landslides Ongoing or progressive movement of Survey and records of known failures slope DYNAMIC TRIGGERING MECHANISMS Rainfall events (e.g., storms, hurricanes, prolonged periods of rainfall) Rainfall data and frequency analysis Seismic events (not currently incorporated in MoSSaiC methodology) Seismograph data and frequency analysis TA BLE 3. 6  Spatial scales of landslide triggering mechanisms, preparatory factors and anthropogenic influences SPATIAL SCALE OVER WHICH VARIATION OCCURS Local/household Hillside Region MECHANISM/FACTOR/INFLUENCE 1m 10 m 100 m 1,000 m 100 km Triggering mechanisms Rainfall Seismic activity Preparatory factors Slope geometry Soils and geology Slope hydrology Vegetation Anthropogenic (aggravating) influences Surface water Groundwater level Slope angle (cut) Load (building) Vegetation Source: Holcombe and Anderson 2010. 9 4    C H A P T E R 3 .   U N D E R S TA N D I N G L A N D S L I D E H A Z A R D • Landslide susceptibility relates to the type slope instability and for confirmation of the and spatial distribution of existing or poten- type of landslide hazard tial landslides in an area. Susceptibility • Empirical rainfall threshold modeling—if assessment is based on the qualitative or sufficient empirical data are available, this quantitative assessment of the role of pre- method can be used in conjunction with paratory factors in determining the rela- susceptibility maps to indicate the potential tive stability of different slopes or zones. timing and spatial distribution of multiple The magnitude and velocity of existing or landslide events potential landslides may be taken into account, but the frequency or timing will • Physically based slope stability modeling— not be specified. the most relevant approach for MoSSaiC, as it allows investigation of the slope stability • Landslide hazard is the probability of a processes and landslide trigger at a scale landslide (qualitatively or quantitatively enabling the identification of appropriate assessed) of a certain type, magnitude, and hazard reduction measures (1–100 m2). velocity occurring at a specific location. Quantitative hazard assessment takes into 3.4.3 GIS-based landslide susceptibility account the role of the triggering event (of mapping a known probability) causing the landslide. Many wide-area and spatially distributed Several different approaches can be used to landslide assessments use GIS software as the assess landslide susceptibility and hazard, platform for assembling digital maps of prepa- including direct geomorphologic mapping, ratory variables such as topography, soils and index-based mapping and heuristic (expert) geology, drainage patterns, and land use. The assessment, inventory-based empirical and data can be augmented and the analysis statistical modeling of slope parameters, and extended if there is a record of the locations of deterministic (physically based) and probabi- past landslides. Landslide inventories allow listic modeling of slope processes (Aleotti and the identification of precedents in which the Chowdhury 1999; Dai, Lee, and Ngai 2002; and influence of each preparatory variable is deter- Huabin et al. 2005; these also contain summa- mined with respect to slope stability and ries of these methods). Table 3.7 outlines the assigned a weighting. Alternatively, experts respective advantages and disadvantages of may assign weights based on their judgment the principal approaches. and experience. The resulting index overlay Selection of the most suitable approach for maps define the landslide susceptibility for a given study must consider the spatial scale each terrain unit. On their own, these GIS- for which it is most appropriate, the data based susceptibility maps cannot be used to requirements, and the level of quantification it predict the exact timing and location of indi- affords (van Westen et al. 2006; van Westen et vidual landslides, but they do provide a vital al. 2008). Four methods of relevance to tool for planning and management in terms of MoSSaiC are briefly reviewed in sections broad zones of relative landslide susceptibility. 3.4.3–3.4.6: An example of GIS capability for develop- ing landslide susceptibility maps is given by • Spatially distributed landslide susceptibil- Nandi and Shakoor (2010). They developed ity mapping using GIS-based methods— relationships between landslides and various useful for the initial identification and pri- instability factors contributing to their occur- oritization of areas with relatively high rence using GIS. A landslide inventory map landslide susceptibility (as described in was prepared using landslide locations identi- chapter 4) fied from aerial photographs, field checks, and • Direct landslide hazard mapping—also use- existing literature. Seven instability factors ful for identification of areas of existing were then selected—slope angle, soil type, soil CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    9 5 TAB L E 3 .7  Advantages and disadvantages of different forms of landslide susceptibility and hazard assessment SCALE METHOD ADVANTAGE DISADVANTAGE S M L Field • Allow rapid assessment taking into account • Totally subjective methodology R Y Y geomorphologic a large number of factors • Use of implicit rules that hinder critical analyses analysis of results Combination of • Solve the problem of hidden rules • Subjectivity in attributing weighted values R Y Y index maps • Total automation of steps to single classes of each parameter • Standardization of data management Logical analytical • Allow the comparison of different slopes • Require monitoring data, preferably from R R Y models • Mathematically rigorous and perfectible installed instruments applicable mainly to slow-speed landslides Statistical • Objective methodology • Systematic collection and analysis of data Y Y R analyses (bivariate • Total automation of steps concerning different factors is quite and multivariate) cumbersome • Standardization of data management Safety factor- • Objective scope and methodology • Need for detailed knowledge of the area R R Y deterministic • Quantitative scope • Use of appropriate geotechnical model approaches requires a lot of experience • Encourages investigation and measurement of geotechnical parameters in detail • Does not take various uncertainties into account Probabilistic • Allow consideration of different uncertain- • Require comprehensive data, otherwise Y R R approaches ties subjective probabilities required • Quantitative scope • Probability distributions difficult especially • Objective scope and methodology for low level of hazard and risk • Provide new insight not possible in deterministic methods Neural networks • Objective methodology • Difficult to verify results when instrumen- R Y Y • Do not require theoretical knowledge of tal data are not available physical aspects of the problem Source: Aleotti and Chowdhury 1999. Note: S = small; M = medium; L = large; R = restricted use; Y = yes. erodibility, soil liquidity index, land cover pat- watershed, the results from the training area tern, precipitation, and proximity to stream— could be extrapolated using the regression that were considered to be of significance in model. This process yielded a landslide sus- terms of landslide occurrence. These were ceptibility map (figure 3.10). imported into the GIS as raster data layers and Basic regression methods for landslide sus- ranked using a numerical scale corresponding ceptibility assessment can be refined by com- to the physical conditions of the region. Fig- puting weight-based combinations of signifi- ure  3.9 illustrates the spatial data for four of cant factors and excluding insignificant factors the presumed independent controlling vari- from consideration; GIS mapping of this type ables. has been widely researched (Lee 2005; Regression analysis was used to associate Nefeslioglu, Gokceoglu, and Sonmez 2008; the occurrence of known landslides with the Van Den Eeckhaut et al. 2006; Van Westen independent slope variables in a subarea of the 2004). watershed (a process known as model train- A GIS environment can also be used as the ing). By assuming that similar slope instabil- platform for simplified deterministic model- ity–related conditions existed in the entire ing of landslide hazard zones or coupling with 9 6    C H A P T E R 3 .   U N D E R S TA N D I N G L A N D S L I D E H A Z A R D FI G U R E 3 .9  Classified spatial factor data a. Slope angle b. Streams c. Soil type d. Land cover Source: Nandi and Shakoor 2010. rainfall forecasts. This form of modeling cal landslides—the relevant features of which requires accurate and detailed spatially dis- might be masked by subsequent land-use tributed data on slope parameters and a high change. level of expertise. Even at the hillside and community scales, direct landslide hazard mapping can be prone 3.4.4 Direct landslide mapping to significant error. Ardizzoni et al. (2002) out- On-the-ground mapping of existing landslides line the potential extent of such errors by com- in areas of known slope instability produces paring hazard mapping results from three maps that can potentially be used for land-use independent mapping teams in a landslide- planning, informing landslide risk manage- prone area of Italy. They found large differ- ment strategies, and creating landslide inven- ences between the landslide hazard maps in tories that can be included in GIS-based land- the form of positional errors (55–65 percent); slide hazard analyses. An experienced these increased significantly when all three mapping team can plot both visible landslide maps were overlaid (~85 percent spatial mis- features and the possible locations of histori- match). Figure 3.11 illustrates the differences CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    9 7 in the teams’ interpretations of the location of F IG U R E 3.1 0  Landslide susceptibility map existing landslides. Information is lacking regarding the uncer- tainties associated with landslide inventory maps (Gallie et al. 2008). Rather than only mapping existing landslides, studies suggest that it may be appropriate for expert mapping teams to identify the topography and other preparatory factors likely to be associated with both existing and future slope failure. In this way, direct mapping of slope features could be Logistic regression used to inform the design of landslide mitiga- susceptibility rating low susceptibility tion measures to address the potential land- medium susceptibility slide causes. high susceptibility very high susceptibility 3.4.5 Empirical rainfall threshold landslide locations in test area modeling Source: Nandi and Shakoor 2010. Historical data on landslides and associated Note: The landslides of the test area are overlaid on the map. rainfall events can be used to establish land- slide probability based on the probability of the triggering rainfall. With sufficient data, the critical rainfall characteristics required to trig- F IG U R E 3.1 1  Three landslide inventory ger landslides can be established for a particu- maps lar region. This is referred to as threshold analysis, and it can be used to predict the Milano landslide expected number of landslides for a particular inventory rainfall forecast. Although this is a useful plan- ning tool, it cannot be used on its own to iden- tify the landslide hazard affecting a specific slope. There are a number of forms that empirical Perugia landslide threshold equations can take depending on the inventory rainfall parameters selected (IRPI 2012). A common form is an intensity-duration equa- tion, which is derived by plotting rainfall intensity (I) against rainfall duration (D) and identifying the threshold above which land- Pavia slides will be triggered. I-D thresholds have landslide the general form inventory  village I = c + α D−ß  road  landslide Where: Source: Ardizzoni et al. 2002. I = Rainfall intensity Note: Maps were surveyed by three independent D = Rainfall duration teams in the Apennines, Italy. Mapped area comprises c ≥ 0 hillside surrounding three small villages. Overall errors in positional mismatch approximately 85 percent. α > 0 ß > 0 9 8    C H A P T E R 3 .   U N D E R S TA N D I N G L A N D S L I D E H A Z A R D Commonly, intensity lies between 1 and 100 mm s−1, duration between 1 and 200 hours, F IGUR E 3 .12  Global rainfall intensity-duration thresholds ß between 2.00 and 0.19, and c = 0 (Guzzetti et intensity (mm/hour) al. 2007; figure 3.12). When c = 0, the threshold 100 7-day threshold 3-day threshold relationship is a simple power law. This nega- 1-day threshold tive power law holds for four orders of magni- tude of rainfall duration (up to durations of 10 500 hours), suggesting a self-similar scaling behavior of the rainfall that triggers landslides (Guzzetti et al. 2007). B A 1 Specific rainfall intensity-duration thresh- C old relationships should be calculated for indi- D vidual regions or countries. For example, for E 0.1 Puerto Rico, I = 91.46D−0.82 (Larsen and Simon 0.1 1 10 100 1,000 1993). duration (hour) Source: Kirschbaum et al. 2009. 3.4.6 Physically based slope stability Note: A = Caine 1980; B = Hong, Adler, and Huffman 2006; C = Crosta and Frattini modeling 2001; D = Innes 1983; E = Guzzetti et al. 2008. To determine the landslide hazard affecting a specific slope, the preparatory and triggering • Numerical models that couple dynamic mechanisms unique to that slope need to be hydrology with limit equilibrium analysis taken into account. This can be undertaken by experts directly mapping slope features in the • Numerical models that represent slope field (heuristic approach; see section 3.4.4). material in terms of its stress-strain behav- Conversely, a quantitative analytical or numer- ior (continuum models) or as particles (dis- ical modeling approach can be applied in crete element models) which geotechnical equations are used to rep- Analytical methods for determining factor of resent landslide processes. safety Many such quantitative approaches express slope stability in terms of its factor of safety (F) which is the ratio between the total Static limit equilibrium methods (analytical or available shear strength of the slope (resisting lumped mass approaches) evaluate the stabi- lizing and destabilizing forces affecting a mass forces) and the shear stresses (destabilizing of material on an observed or assumed poten- forces). tial failure surface (known as the slip surface or shear surface). The slope is analyzed as a F = available shear strength of slope shear stress acting to destabilize slope two-dimensional cross-section, and the mate- rial above the slip surface is typically divided (discretized) into vertical slices. The stabiliz- F = 1 Marginally stable slope ing and destabilizing forces acting at the base F < 1 Unstable slope of each slice (at the slip surface) are calculated F > 1 Stable slope for a single point in time and take into account the angle of the slip surface at the slice base, There are three broad types of physically the weight of the slice material, loading on top based modeling that may be used to determine of the slice (such as buildings or vegetation), slope stability; these are as follows, in order of the effect of pore water pressure, and the shear increasing complexity: strength of the material (cohesion and angle of • Analytical methods for calculating factor of internal friction). F is then calculated for the safety (static limit equilibrium methods) entire slip surface. CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    9 9 Different limit equilibrium methods are • Along the slip surface, the material will employed according to the assumed geometry exhibit failure according to the specific cri- of the landslide failure surface: teria selected for representing shear strength (the Mohr-Coulomb criteria for • Single plane (or slightly curved), usually elasto-plastic failure is typically used for shallow translational slides in steep slopes soils). • Circular, uniform strata or deep soils and • At the moment of failure, the shear strength small to medium-size rotational landslides is fully mobilized along the length of the (figure 3.13) slip surface. • Double or triple wedges, medium to large • The water table location (and hence, the translational landslides. pore water pressure field) is static and is Figure 3.13 shows the method of slices defined by the user. (Ordinary and Bishop methods) represented • Different assumptions are made about the on a sample slope in which it is assumed that interslice forces, depending on the method. failure will occur by rotation of a block of soil on a cylindrical slip surface. (See Nash 1987 for • Behavior of the slope material once failure a review of different limit equilibrium meth- has occurred is not accounted for. ods.) Limit equilibrium analysis requires several The results of the factor of safety analysis simplifying assumptions to be made to calcu- are of limited value in themselves, as they late F: depend on the simplifying assumptions of the method adopted, the parameter values • A slope will fail as a coherent mass of mate- selected, the water table location, slip surface rial sliding along a specific two-dimen- geometry and location, and the discretization sional slip surface defined by the user of the slope. For example, in figure 3.13, the (stress-strain relationships and three- Bishop method gives an F of 1.52, while the dimensional effects involved in the mechan- Ordinary method of slices gives an F of 1.43. ics of failure are not represented). Note that a factor of safety of 1 does not neces- sarily indicate that failure of the slope is immi- nent. Moreover, the real factor of safety is FI G U R E 3 .13  Discretization of a slope into slices to facilitate slope influenced by many variables that are not nec- stability calculations essarily represented in the slope stability F = 1.43 calculated slice weight w = b ∑ (γi hi) model, such as minor geological or soil details, using the Ordinary and progressive failure of the slope, among c = 4.8 kN/m2 method of slices trial slip circle many others (Nash 1987). Φ = 35 degrees Soil 1 h1 F = 1.52 calculated γ = 17.3 kN/m2 using Bishop’s c = 35.9 kN/m2 Dynamic slope hydrology and limit equilibrium Soil 2 h2 models modified method Φ = 0 degrees γ = 17.3 kN/m2 The second type of slope stability model sig- nificantly advances the static analysis methods 10 m by dynamically integrating external “forcingâ€? scale silty variables (landslide triggering factors) such as sand rainfall and slope hydrology, so that slope sta- clay bility can be analyzed over a period of time. firm soil Although there are fewer commercially avail- able integrated dynamic hydrology and limit Source: Turner and Schuster 1996; © National Academy of Sciences, Washington, DC, 1966. Reproduced with permission of the Transportation Research Board. equilibrium models than static limit equilib- rium models, they are an improvement over 1 0 0    C H A P T E R 3 .   U N D E R S TA N D I N G L A N D S L I D E H A Z A R D the classic limit equilibrium method in the fol- scale from blocks to grains) using a force- lowing ways: based approach. Although some of these models are com- • Groundwater conditions are dynamically mercially available, their data requirements, modeled over time in terms of saturated model sensitivity, and complexity can pose sig- and unsaturated flow, positive and negative nificant challenges to their application. pore water pressures, and rainfall. These dynamic processes are particularly influen- tial in deep tropical residual soils. 3.5 SLOPE STABILITY VARIABLES • Limit equilibrium methods, such as Bishop and Janbu for circular or noncircular fail- This section provides a more detailed descrip- ure, are applied using a search method to tion of the main slope stability variables intro- identify the minimum F surface at specific duced in section 3.4.1—preparatory factors, times during the dynamic hydrology simu- triggering mechanisms, and anthropogenic lations. (aggravating) factors—in terms of their identi- fication and measurement, and their influence Some limitations of dynamic hydrology on slope stability. This information is the basis models relate to the simplifying assumptions for the process of community-based slope fea- used in the calculation of groundwater flow, ture mapping, landslide hazard assessment, which means that these models cannot repre- and design of landslide hazard reduction mea- sent soils with complex or highly spatially sures detailed in chapters 5 and 6. variable flow patterns. Limitations in the sta- Different slope variables may contribute to bility component are related to those inherent the shear strength of the slope (stabilizing in limit equilibrium analysis. forces) or to the shear stresses acting on the The value of this type of dynamic slope sta- slope (destabilizing forces). Some variables bility model is that it allows slope processes may contribute to both shear strength and dominating the stability of a particular slope to shear stress. The way in which each variable be explored. operates can be complex and may change over time with natural processes (such as hydro- Continuum and discrete element models logical variations) or human activities. For Continuum models use distinct rheological example, figure 3.14 shows preparatory factors formulas known as constitutive equations to that could have potential roles in slope insta- describe the behavior of a particular soil type bility, illustrating a variety of subsurface routes under dynamic stress and strain conditions. infiltrating surface water may take. Differ- Therefore, in these models, the shear zone ences in soil water flow paths can lead to “evolvesâ€? (rather than being artificially delayed or rapid slope instability responses to imposed in terms of geometry or location) rainfall. according to the geometry of the slope, the ini- The role of these variables in affecting slope tial conditions applied, and the particular rhe- stability may be assessed qualitatively or mea- ology of the material. sured and used as an input in a quantitative Related to the continuum approach are slope stability assessment. macroscale discontinuous deformation analy- sis models, which allow for the local deforma- 3.5.1 Rainfall events tion of shear zones and the overall slope while Rainfall-triggered landslides are the result of accounting for strong discontinuities and surface water infiltration, increased pore detachment of mesh elements. Conversely, water pressure, and a reduction of the shear distinct (or discrete) element methods repre- strength of the slope material. The particular sent the movement of rigid elements (on a combination of preparatory variables and CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 0 1 F IG U R E 3.1 4  Preparatory factors that can influence slope stability rock cliffs 100% water ingress runoff infiltration to through fractures, rock mass root holes etc. partially clay-infilled joint overland rapid recharge down fault following intermittent water into flow zone (days/weeks) slope movement tension crack drop in velocity causes local perched slow sediment deposition in water dike infiltration and active channel throughflow original precut weathered dike aquitard water table fault original ground rise in main surface water table cut seepage pressures induce spring piping along joints and cutting induces high recharge into saprolite through weak materials, hydraulic gradient and from underlying rock allowing relatively rapid flow internal erosion through system (days) Source: Hencher, Anderson, and Martin 2006. rainfall characteristics will determine which Summary: assessment of rainfall events slopes fail. Not all rainfall events will trigger land- • Rainfall events should be described in slides, and not all slopes will fail as a result of a terms of their intensity (mm/h) or total vol- particular event. The intensity and duration of ume (mm), and their duration (h). the rainfall event will determine its effect on a • Rainfall data may be recorded by manual or specific slope. A short, intense rainfall event automatic rain gauges. may have less impact than a longer-duration, less intense event if the hydraulic conductivity • Government ministries and meteorological of the slope is low. It is the hydraulic conduc- organizations usually collect some form of tivity of the slope that determines how much daily or hourly rainfall data. rain infiltrates and how much is retained as • Satellite and radar data can be interpreted surface runoff. Conversely, prolonged very to determine rainfall intensity. low–intensity rainfall may have little effect on a slope with a high hydraulic conductivity, Records should be obtained for all major since the infiltrated water will be rapidly con- rainfall events, in particular the generally heavy veyed through the subsurface without saturat- rainfalls that are associated with hurricanes, ing the soil. tropical storms, and tropical waves (figure 3.15). 1 02    C H A P T E R 3 .   U N D E R S TA N D I N G L A N D S L I D E H A Z A R D FI G U R E 3 .1 5  Hurricane Tomas over the Eastern Caribbean, 2010 Source: National Oceanic and Atmospheric Administration. 3.5.2 Slope angle • not be precise enough to determine slope angles over small distances. Slope angle is one of the key determinants of slope stability. The greater the slope angle, the greater the shear stresses acting on the slope. Slope angle can be efficiently measured However, the relationship between slope angle with a low-cost instrument such as an Abney and slope stability is not straightforward, since level (figure 3.16a), which consists of a fixed the stabilizing forces (the shear strength of the sighting tube, a movable spirit level connected slope) will be determined by variables such as to a pointing arm, and a protractor scale. The material type and strength, water table height, instrument is held at eye level in order to and the influence of loading and vegetation. “sightâ€? a colleague of the same height either Thus, shallow slopes with deep, weak soils can up- or downslope; alternatively, a ranging pole be less stable than steeper slopes comprised of can be marked at eye height (figure 3.16b). shallower soils or exposed bedrock. Accurate slope angle determination is more When assessing slope angles from existing difficult in communities where there is high topographic maps, the accuracy and precision housing density or dense vegetation (fig- of the contours needs to be taken into account ure 3.17), or where previous landslides (which can result in significant ground disturbance) since the contours may have occurred. In such cases, ensuring that the • be interpolated and therefore inaccurate steepest slope segments have been identified with respect to the actual topography (par- requires particular care. At a later stage in the ticularly areas of slope plan convergence project, a more comprehensive topographic and divergence), and/or survey may be required to confirm slope CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 0 3 angles, distances, and drain gradients (see F IG U R E 3.1 6  An Abney level and its use chapter 6). Summary: assessment of slope angle • Estimating local slope angles from topo- graphic maps is likely to be imprecise. • Use an Abney level, theodolite, total station, or similar instrument to measure slope a. Abney level. angles. • Dense vegetation may mask the true topog- raphy. 3.5.3 Material type and properties Material type plays a significant part in deter- mining which slopes are susceptible to land- slides. In assessing the influence of slope material on stability, three broad characteris- tics need to be determined: • The depth and location (strata) of different material types on the slope • The strength of the materials • The hydrological properties of the materials Soil formation b. Abney level being used to measure slope angle. In the tropics, rock is weathered relatively rap- idly due to the high temperatures and humid- ity; this can result in the formation of deep F IG U R E 3.1 7  Slope benched by resident to soils over weakened bedrock. The first stage in build a house assessing the influence of materials on slope stability is therefore to estimate the approxi- mate depth of soil and weathered material. The MoSSaiC methodology addresses slopes where the dominant surface material is resid- ual soil. Weathering and strength The typical weathering profile of tropical soils is commonly expressed in terms of six weath- ering grades (figures 3.18 and 3.19). Dense vegetation above the benched slope The weathering grade of slope material can and a major failure below the property can be considered a surrogate for strength: gener- make it more difficult to estimate the hillslope ally, the greater the weathering from rock to segment slope angles. soil, the weaker the material. The strength of residual soils can vary greatly depending on its parent material (composition). Soils can be 1 0 4    C H A P T E R 3 .   U N D E R S TA N D I N G L A N D S L I D E H A Z A R D FI G U R E 3 .1 8  Typical weathering profiles of tropical soils Humus/topsoil VI Residual All rock material converted to soil; mass structure and material fabric soil destroyed. Signiï¬?cant change in volume. V Completely All rock material decomposed and/or disintegrated to soil. weathered Original mass structure still largely intact. IV Highly More than 50% of rock material decomposed and/or disintegrated to soil. weathered Fresh/discolored rock present as discontinuous framework or corestones. III Moderately Less than 50% of rock material decomposed and/or disintegrated to soil. weathered Fresh/discolored rock present as continuous framework or corestones. II Slightly Discoloration indicates weathering of rock material and discontinuity surfaces. weathered All rock material may be discolored and weaker than its fresh condition. IB Faintly Discoloration on major discontinuity surfaces. weathered IA Fresh No visible sign of rock material weathering. Idealized weathering proï¬?les - without corestones (left) and Rock decomposed to soil with corestones (right) Weathered/disintegrated rock Rock discolored by weathering Fresh rock Source: Fookes 1997, reproduced with permission of the Geological Society, London. Weathering grades are based on the commonly used classification of Fookes 1997, Komoo and Mogana 1988, and Little 1969. Hydrological properties characterized in terms of particle size distri- bution and structure; bulk density; the ratio of The strength of soils and weathered materials sand, silt, and clays; and the chemical compo- will be affected by moisture content. Increased sition of the clay. These characteristics can be moisture content of slope material causes used as proxies for strength and hydrological increases in pore pressure, which reduces properties based on empirical relationships shear strength. Conversely, the drying of slope (Carter and Bentley 1991). material can cause negative pore pressures For slope stability analysis, a more precise (matric suction), which increase shear measure of soil strength entails laboratory strength (Fredlund 1980; Fredlund and assessment of the geotechnical properties of Rahardjo 1993). The magnitude of pore pres- slope soil samples (figure  3.20). The shear sures associated with wetting and drying are strength of a specific soil can then be described dictated by material properties such as pore in terms of soil cohesion (c, kPa) and angle of size and chemistry. For instance, clay particles internal friction (Φ, degrees), which are the carry a negative charge, which influences the parameters that need to be specified in ana- retention of moisture in the pores. Thus, sandy lytical and numerical slope stability models porous soils may experience little variation in (Nash 1987). strength, while the strength of clay soils can In areas where landslides have already vary significantly with moisture content. occurred, the slope material will have a much The deep residual soils of the humid tropics lower strength than its original intact strength; can often have relatively high hydraulic con- this is its residual strength. ductivities, allowing rainfall to infiltrate rap- CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 0 5 idly. Periods of rainfall can result in the forma- F IG U R E 3.1 9  Weathering profiles tion of saturated zones within the soil strata nearer the ground surface. Different material types, when saturated, will exhibit different hydraulic conductivities depending on their structure and composition. In unsaturated conditions, hydraulic conductivity will vary as a function of moisture content. Subsurface water flows within soil pores can be augmented by the development of a network of wider-diameter pipes within the soil (figure 3.21). Soil pipes can be a contribu- a. Grade II material transitioning to Grade III tory factor to landslides by giving rise to locally above. high pore water pressures (Brand, Dale, and Nash 1986; Pierson 1983; Uchida 2004). The effect of pipe flow is also spatially complex— reducing pore pressures in the upslope area covered by the pipe network, while increasing pore pressures in downslope locations, espe- cially if the pipe network is blocked. Sharma, Konietzky, and Kosugi (2009) report numeri- cal model results summarizing this complex relationship. F IGUR E 3 . 2 1  Exposed soil pipe some 30 cm below the soil surface b. Indication of abrupt change in weathering grade from V to VI above. F IG U R E 3. 2 0  Shear box used to determine soil strength parameters Summary: assessment of slope material types and properties • The dominant slope material type can often be determined by referring to soil and geo- logical surveys available from government engineering departments or similar organi- zations. 1 0 6    C H A P T E R 3 .   U N D E R S TA N D I N G L A N D S L I D E H A Z A R D • More precise assessments of material types and Kneale 1982). Since soil water flow takes and strata can be made in the field through place at right angles to the lines of total poten- direct observation, boreholes, or soil pits. tial, soil water flow lines can—again as an approximation—be drawn at right angles to • Material strength can be inferred from topographic contours. It is this logic that gives weathering grades. rise to the construction of potential zones of • Basic descriptions of material characteris- soil water convergence and divergence on a tics can be used to infer strength and hydro- hillslope, as shown in figure 3.22. The two logical properties, using the findings from locations A and B depict zones of convergence numerous studies in the scientific and engi- and divergence, respectively; much higher neering literature. pore water pressures will be anticipated in the former case (due to the concentration of flow), • Areas where there have been previous land- with lower pore water pressures (perhaps slides will have lower (residual) material unsaturated conditions) in the zone of diver- strength. gence. • The specific geotechnical properties (c, Φ) Subtle topographic hillslope hollow fea- of a material can be measured by triaxial or tures (zones of convergence) are important to shear box testing. locate since they represent areas of potential slope instability because of the relatively higher • Material hydrological properties can be pore water pressures, which in turn serve to measured using equipment such as a reduce soil shear strength. This means that permeameter or infiltrometer. failures can occur on relatively shallow slopes, • Pore pressures and subsurface water levels triggered by soil water convergence taking can be measured in the field using a peizo- place upslope. Figure 3.23 shows an example of meter. such a failure on an 18-degree slope; slopes above, with slope angles as high as 45 degrees, 3.5.4 Slope hydrology and drainage remained stable since they lacked the same The dynamic nature of a slope’s response to surface water infiltration and subsurface flows make an understanding of the overall hydrol- F IGUR E 3 . 2 2  Definition of the planimetric ogy of a slope essential for gaining insights into contributing area at two locations in a its stability. hypothetical landscape Convergence zones It is important to identify zones of topographic convergence—elements of the slope that are concave in plan. Convergence zones concen- trate surface water flows and strongly influ- ence subsurface water flows. A Water moves through soils according to the total potential of soil water, being the sum of the gravitational potential (the elevation of the point in the soil above some arbitrary datum) and the pressure potential (either positive or B negative soil water pressure). Other than for the shallowest slopes, topographic contours Source: Iverson 2000. can be considered an approximation of the Note: Blue = planimetric contributing areas; brown lines = topographic contours, with lowest elevations lines of total potential (in that the gravitational at bottom left. potential dominates the equation—Anderson CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 0 7 • High vegetation densities may disguise top- F IG U R E 3. 2 3  Shallow rotational slip on an ographic features. 18-degree slope at the foot of an extensive hillside • Existing contour maps may incorrectly por- tray the detailed slope topography. The following effects of vulnerable unau- thorized communities on drainage should also be noted: • Addition of water to the slope by house- holds (point water sources) • Altered drainage patterns, incomplete drains, or uncontrolled flows • Zones of saturation created by housing structures, modified slope angles, and access degree of topographic convergence, and hence alignments such as footpaths or roads retained lower pore pressures. 3.5.5 Vegetation Urban slope drainage Population growth, urbanization, and poverty Although vegetation may generally have a pos- have led to the development of large vulnerable itive effect on slope stability, it can reduce the communities on steep slopes in many tropical stability of slopes in some cases. areas. If there is a publicly provided piped water Beneficial and adverse effects supply, but no drainage, the discharge of water from houses onto the slope can be significant, Vegetation can influence hydrological and especially when housing density is high. mechanical slope stability mechanisms Sources of water from properties include (table 3.8). gray water from kitchens and bathrooms, leak- In vulnerable urban communities, slope age from supply pipes, and septic tank dis- stability may be influenced by changes in slope charges. The construction of houses, foot- vegetation, such as the following: paths, and drains can change surface and • Removal of deep-rooted vegetation that subsurface water flow patterns on the slope— may have had a stabilizing effect on the typically concentrating them at certain loca- slope material through root reinforcement tions or resulting in zones of constant satura- and uptake of water from the soil tion. Figure 3.24 illustrates a range of common conditions that require identification and • Cultivation of water-demanding plants assessment of their impact. Surface water (such as dasheen; figure 3.25a) that require management measures can then be designed irrigation or the deliberate retention of water on the slope in trenches or terraces—this to improve slope stability. This process is increases infiltration and soil pore water explained in chapters 5–7. pressures, thus reducing soil shear strength Summary: Assessing slope hydrology and • Cultivation of shallow-rooted plants (such drainage as banana and plantain) that add loading to the slope and disturb the soil structure • Shallower slopes at the base of hillsides (increasing soil permeability) without add- may be as, or even more, susceptible to ing root tensile strength landslides as the steeper slopes above because of the convergence of surface and • Planting certain vegetation species for the subsurface water. specific purpose of stabilizing slopes (bio- 1 0 8    C H A P T E R 3 .   U N D E R S TA N D I N G L A N D S L I D E H A Z A R D FI G U R E 3 .24  Common drainage issues in unauthorized communities a. Unauthorized housing is often supplied b. Slope failure caused by lack of water c. A water tank constructed of a single with water delivered through plastic management from upslope unauthor- skin of blocks which failed and caused pipes. ized housing. significant downslope damage. Such structures have the potential to trigger slope instability. d. A drain that is incomplete and may e. Small footpath drain rendered f. Damaged roof guttering discharging thereby cause instability downslope. completely ineffective by routing water to poorly configured drain at the foot supply pipes along its length. of a retaining wall. g. Household septic tank discharging h. High-volume discharges from washing i. Shower and hand-washing water directly into the slope. machines. discharging onto the slope, leading to saturated soil and stagnant water. CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 0 9 TAB L E 3 .8  Vegetation influences on slope stability STABILITY VEGETATION MECHANISM EFFECT DESCRIPTION Rainfall interception on foliage increases evaporative losses and reduces infiltration into the slope material Beneficial Uptake of soil water by roots reduces the water content of slope material and therefore reduces pore water pressures Roots increase soil permeability Hydrological Soil moisture depletion may cause desiccation cracking and increase soil permeability Adverse Stem flow and live or decaying roots can generate preferential flow paths within the slope material (macropores and soil pipes), thus increasing the concentration of water in certain locations, particularly if the water is directed to the soil-rock interface, which is a common zone of weakness Roots can provide soil reinforcement and increase soil shear strength Beneficial Tree roots may anchor into firm material at depth and have a buttressing effect in resisting Mechanical the shallow movement of soils Trees are subject to “wind throwâ€? which exerts a force on the slope during high winds Adverse Large trees will significantly increase the loading on the slope engineering); for example, vetiver grass is Vegetation effects on slope stability are thus widely used for its extensive root network complex, being dependent on the nature of the and slope-stabilizing properties (fig- slope and vegetation species. For this reason, ure 3.25b). the relative influence of each of the factors in F IG U R E 3. 2 5  Examples of adverse and beneficial effects of vegetation on slopes a. Water-demanding plants, such as dasheen, the large-leafed plants on the right, may be cultivated in naturally saturated areas, or water may be retained on slopes for this purpose. b. Roots of vetiver grass can grow to some 3 m. 1 1 0    C H A P T E R 3 .   U N D E R S TA N D I N G L A N D S L I D E H A Z A R D table 3.8 will vary from slope to slope. Conse- • The succession of plants on a particular quently, “it is not sufficient simply to classify part of a slope can indicate the location of a individual mechanisms, they must be quanti- previous landslide. fied. Only then can the net influence of vegeta- 3.5.6 Loading tion be clarified and its influence on stability be definedâ€? (Greenway 1987, 192). Construction adds to slope loading, increases the shear stresses acting on the slope, and thus Vegetation as an indicator of past landslides contributes to destabilizing forces. The succession of plants on a particular part of Construction materials and loading a slope can indicate the location of an earlier slope disturbance—an abandoned cultivated In vulnerable communities, unauthorized area, the site of a fire, or a landslide. In the houses are typically enlarged in an incremental tropics, landslide scars and debris will revege- manner. Often, there is a progression from tra- tate within a short time if the soil depth is suf- ditional wooden structures to heavier concrete ficient and nutrients are available (for instance, construction (figure 3.27). This incremental from decomposition of the vegetation mixed construction increases slope loading in terms of into debris or from erosion). Figure 3.26 pres- the weight of the construction material. ents a model of post-landslide vegetation suc- Construction on former landslide zones cession for the Caribbean showing the rela- tionship between slope stability, soil organic A landslide significantly reduces the strength matter, and slope revegetation. of failed slope material—not just along the slip surface, but also within the failed mass. Con- Summary: Assessing vegetation cover struction on previously failed material is com- mon in rapidly developing unauthorized urban • Discussions with local botanical specialists areas in the tropics and may occur immedi- may help establish the net influence of veg- ately after a landslide or several years later etation and local planting practices on slope (figure 3.28). Rapid reconstruction on the site stability. of a landslide reflects the severe pressure for • The presence of certain species on slopes housing that can lead to residents discounting can indicate either natural or manmade the hazard, in full knowledge of past failure. In saturated conditions. the case of historic landslides, the majority of FI G U R E 3 .26  Model of post-landslide vegetation succession for the Caribbean newly exposed nonvascular plants mineral soil unstable pioneer trees residual forest pioneer shrubs soil landslide climbing ferns mature forest soil newly exposed grasses, herbs pioneer trees mineral soil pioneer trees stable residual forest pioneer shrubs mature forest soil 0.1 1 10 100 1,000 landslide age (years) Source: Walker et al. 1996. Note: Four plant succession pathways for landslides in a low-elevation forest in Puerto Rico. On unstable soils, erosion constantly resets succession (dotted lines). On stable soils, filled squares indicate age at which pre-landslide vegetation may reestablish. CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 1 1 F IG U R E 3. 2 7  Examples of incremental construction a. Additional loading of a 55-degree slope with an b. Property enlarged by building outside the already high housing density increases landslide risk. existing walls. the community may be unaware of past slope 3.6 SCIENTIFIC METHODS FOR history and the associated potential hazard. In ASSESSING LANDSLIDE both cases, the effect of construction in such HAZARD locations is to reduce slope stability in all the ways discussed here, potentially reactivating a To assess the landslide hazard affecting a par- landslide or triggering new ones. ticular hillside community requires a method that can account for the roles of the different Summary: Assessing loading and former slope stability variables described in the pre- landslides vious section at the correct scale and over time. This assessment can indicate potential • Housing density and construction type can landslide hazard mitigation strategies such as be rapidly assessed from aerial photo- surface water management for intercepting graphs. rainfall runoff and household water, and • More detailed site surveys will reveal the reducing infiltration (the approach taken by interaction between loading and slope mate- MoSSaiC). rial. In section 3.4, physically based slope stabil- ity models noted as being particularly relevant • Areas of very old large landslides may have for MoSSaiC were those that represent slope become masked by dense vegetation growth mechanical processes and dynamic hydrologi- and subsequent construction. cal processes at local hillside/community • An integrated interpretation of local geol- scales. Many of the slope stability variables ogy, topography, variations in soil depth, described in section 3.5 are used as inputs to boulder locations, and vegetation can help physically based models, thus allowing their identify landslides that occurred before liv- relative roles in determining slope stability to ing memory. be analyzed. The community-based mapping 1 1 2    C H A P T E R 3 .   U N D E R S TA N D I N G L A N D S L I D E H A Z A R D FI G U R E 3 .28  Examples of reconstruction on former landslide sites a. Unauthorized housing built on a preexisting b. Houses built on the site of a landslide that landslide within one year of the failure having affected the whole hillside approximately 90 taken place. years previously. and measurement of these variables is a particular slope. If surface water infiltration described in chapter 5. from rainfall and piped water supplies is the This section introduces three physically driving factor in slope failure, this form of based (scientific) methods for assessing land- simulation can allow the potential effective- slide hazard. ness of surface drainage to be investigated. The use of coupled hydrology-stability mod- • Coupled dynamic hydrology and slope els is an important part of the design and sci- stability models to simulate physical pro- entific justification of any drainage measures cesses affecting slope stability over time aimed at reducing the landslide hazard. Esti- (including dynamic hydrology), identify mating the impact of surface water infiltra- dominant landslide causes, and predict tion—and thus the effectiveness of potential landslide hazard (probability, magnitude, drainage measures—demands a numerical location) model that incorporates dynamic hydrology • Resistance envelope calculations to so the slope stability response can be simu- determine whether negative pore pressures lated over time. are required to maintain the stability of a Several numerical models are available that slope would allow such an analysis (see http://www. ggsd.com). One example is CHASM (Com- • Static analysis of retaining walls to deter- bined Hydrology and Slope Stability Model) mine the stability of retaining walls. software, which has been developed by the The above is not intended to be an exhaus- authors and used in numerous research and tive list of landslide hazard assessment meth- practical applications to date, including ods, but rather demonstrates the level of pro- MoSSaiC. The following overview of CHASM’s cess representation that is required and that structure and capabilities is based on this can be realistically achieved in the context of experience and is in no way intended as an MoSSaiC. endorsement. The overview may assist the MCU in discussions regarding the selection of 3.6.1 Coupled dynamic hydrology and appropriate slope stability models. It is beyond slope stability models the scope of this text to review the suitability Coupled dynamic hydrology and slope stabil- of all such potential models for particular ity models can allow the identification of applications. In any event, it is likely that local those processes that dominate the stability of engineers will be familiar with, and have CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 1 3 access to, other slope stability models that may the dynamic rainfall conditions for each be suitable for MoSSaiC interventions. hour of the simulation. Model configuration • The slip surface search mode is also defined, searching for the location of either a circu- The main features of CHASM are described in lar or noncircular slip surface with the low- Anderson et al. (1996, 1997) and Wilkinson, est factor of safety. Brooks, and Anderson (1998, 2000), among others. Figure  3.29 shows how a slope cross- Dynamic hydrology component section is represented in CHASM; the princi- ple equation set is given in section  3.7.4. The Within CHASM, infiltration during rainfall is simulation is configured as follows: calculated using Darcy’s Law; vertical flow in the unsaturated zone is computed using Rich- • The slope is divided into regular columns ards’ equation solved in explicit form inside and cells, the centers of which form compu- vertical columns. Within the integrated model tational points for the solution of equations structure, the hydrology scheme represents for slope hydrology. slope plan curvature (convexity and concav- • Each cell is assigned a material type, and ity) by varying the breadth of the columns (fig- the strength and hydraulic properties of ure 3.30). The pseudo-effect of the three- each material are specified (in this example, dimensional topography on water fluxes can there are three material types). thus be investigated and its impact on stability estimated (GCO 1984). • Vegetation, slope loading, and point water sources can be defined for specific surface Slope stability component cells. At the end of each simulation hour, the pore • Hydrological boundary conditions are pressure field generated by the hydrology defined—the initial estimated position of component is used as input to standard two- the water table, the initial moisture content dimensional stability analyses where the slip of each cell, the initial surface suction, and surface is located within the midplane of the three-dimensional structure. CHASM uses Bishop’s (1955) simplified circular method FI G U R E 3 .29  Representation of a slope cross-section for analysis with an automated search procedure (Wilkin- in CHASM software son, Brooks, and Anderson 2000), or Janbu’s noncircular method for estimation of the precipitation slope’s factor of safety (Nash 1987). Pore pres- evaporation slip search grid sures, both negative and positive, are incorpo- runoff rated directly into the effective stress determi- nation of the Mohr-Coulomb equation for soil shear strength. This allows derivation of the slip circle minimum factor of safety with temporal varia- slope profile for stability model tions arising from hydrodynamic responses and changes in the position of the critical slip soil 1 surface (Wilkinson 2001). modeled water table Other useful features for identifying hazard soil 2 drivers CHASM’s numerical scheme includes a sur- soil 3 face cover model, which allows investigation of the hydrological and geotechnical effects of vegetation on slope stability. Vegetation 1 1 4    C H A P T E R 3 .   U N D E R S TA N D I N G L A N D S L I D E H A Z A R D affects slope stability through rainfall inter- ception, evapo-transpiration, changes in F IGUR E 3 . 3 0  CHASM representation of a natural hillslope hydraulic conductivity, root reinforcement, noncircular and surface loading—all of which are included slip search R ET in the model (Collison 1993; Wilkinson, Brooks, and Anderson 1998; Wu, McKinnell, and Swanston 1979). RO Piped water is often supplied to hillside I communities. In unauthorized communities, WT there is usually no drainage or sewerage provi- evaporation & rainfall Q transpiration interception sion, so gray water from sinks and bathrooms is discharged directly to the slope. Foul water drainage goes to a septic tank or pit latrine usually within a few meters of the property, R rainfall leaf ET evapotranspiration the outflow from which returns directly to the drip RO runo slope. It is possible within CHASM to assign stemflow I inï¬?ltration Q lateral flow leakage at defined points on the slope surface water uptake WT water table with specified flux rates by increasing the by roots effective rainfall to the grid columns where runo water leakage into the slope has been identi- increased fied. inï¬?ltration Unauthorized housing density can deep percolation approach 70 percent of the surface area of slopes—adding significant loading. Building Source: Adapted from Wilkinson et al. 2002. loads need to be taken into account when establishing comparative influences on slope stability. In Bishop’s method, loading is incor- porated by increasing the weight of the slices D.C., in 2010. The simulation time-step shown on which the buildings are located. here is toward the end of a 1-in-100-year, 24-hour rainfall event, in which the factor of Interpreting simulation results safety has fallen from approximately 1.32 to For each computation time-step of the simula- 1.28. Perched water tables are visible at the tion, the typical outputs of models such as interface between the upper two soil strata. By CHASM include the end of the storm, F is predicted to be approximately 1.25 before recovering as the • predicted slip surface location, water table drops. Although a landslide is not • pore water pressure and soil moisture fields predicted (F > 1), the weakest part of the slope throughout the slope, and can still be identified from the location of the slip circle. • factor of safety. Slope stability models with features similar These outputs can often be directly visual- to those outlined above, and that include the ized in the model’s graphic user interface or dynamic modeling of pore pressure conditions may simply be in the form of text files. Text file (both positive and negative), allow determina- outputs can be graphically represented using tion of the impact of rainfall as a landslide trig- standard software such as R, Matlab, or IDL. gering mechanism. Using a model with these Figure 3.31 presents the graphical representa- attributes, an assessment can be made of the tion of CHASM outputs using open source likely impact of surface water management as software developed by volunteers at the Ran- a means of contributing to improving slope dom Hacks of Kindness event in Washington, stability. CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 1 5 PHYSICALLY BASED SLOPE STABILITY MODELS • Simulation of the physical processes affecting slope stability USAGE • Identification of dominant landslide causes • Landslide hazard prediction (probability, magnitude, location) SOURCE See http://www.ggsd.com for a comprehensive listing of slope stability software FURTHER See section 5.6.3 for CHASM application DISCUSSION 3.6.2 Resistance envelope method for which the slope may be expected to remain determining suction control stable (Anderson, Kemp, and Shen 1987). The resistance envelope method can be used In the resistance envelope method, several to determine whether negative pore pressures slip surfaces are assumed and the average are required to maintain the stability of a slope. shear strength required for equilibrium is The apparent significance of slope drainage determined (using an appropriate method of can be corroborated using resistance enve- analysis, such as Bishop 1955) along each of lopes to identify the controls on slope stability the surfaces, together with the corresponding (Chowdhury, Flentje, and Bhattacharya 2010; average normal stress. The average mobilized Fredlund 1980; Janbu 1977; Kenny 1967). shear strength is then plotted against the aver- Resistance envelope calculations can be used age effective normal stress, with each point on to show either the average negative pore pres- the plot representing a critical slip surface. sure required for the maintenance of stability Joining all these points together forms the or, conversely, the saturated conditions under resistance envelope, onto which the plot of the F IG U R E 3. 31  Outputs from a CHASM simulation Slope Factor of Safety and Precipitation 1.26 16 1.24 14 precipitation mm h−1 1.22 12 factor of safety 1.2 10 1.18 8 1.16 6 1.14 4 1.12 2 1.1 0 0 50 100 150 200 250 300 350 hours Source: Prototype visualization software created at Random Hacks of Kindness event 2010. 1 1 6    C H A P T E R 3 .   U N D E R S TA N D I N G L A N D S L I D E H A Z A R D shear strength of the soil can be superimposed can reasonably be attributed to infiltration (Chowdhury, Flentje, and Bhattacharya 2010). controls. The methodology assumes negative pore pres- sures act directly in effective stress terms. Fig- 3.6.3 Modeling the impact of small ure 3.32 provides a generalized illustration of retaining walls the superimposition of the resistance envelope Many residents in vulnerable communities and the laboratory-determined soil strength seek to reduce landslide risk by constructing envelope for a case in which the slope is single-skin, reinforced block retaining walls dependent upon soil suction (negative pore (figure 3.34). Such walls are common because pressures) for stability. they can be constructed at the household level, Application of the method to a site in the require no community consensus or govern- Eastern Caribbean is illustrated in figure 3.33. ment permission, and can be built progres- Using two different pairs of values for the geo- sively as the resident accumulates funds to technical properties (effective cohesion, c', purchase materials. But even if they are expe- and effective angle of internal friction, Φ'), obtained from two separate sites on the slope, F IGUR E 3 . 33  Resistance envelope plots the results suggest that the slope must be shear strength kPa maintained at either 50 • marginal negative pore pressure (fig- 40 ure 3.33a; c' = 10 kPa, Φ' = 20 kPa), since for normal loads in excess of 50 kPa, the resis- 30 tance envelope shows marginally greater 20 lab results shear strength is required for stability than can be mobilized by the slope material (as 10 resistance envelope indicated by the laboratory shear strength 0 values used); or 0 10 20 30 40 50 60 70 normal load kPa 80 90 100 • very low positive pressures (figure 3.33b; a. The graph shows negative suction is required c' = 10 kPa, Φ' = 25 kPa). to bring the mobilized shear strength equal with the resistance envelope (for normal loads > 50 kPa; for material properties c' = 10 kPa, It is to be inferred that significant rainstorm Φ' = 20 kPa). events will, through lack of drainage provision on the slope, increase pore pressures beyond shear strength kPa 60 those limits, thus suggesting that instability 50 40 FI G U R E 3 . 32   Superimposition of resistance 30 and strength envelopes lab results 20 saturated strength S2 envelope 10 Fmin = shear strength, Ï„, kPa S1 dry resistance envelope resistance envelope 0 S2 0 10 20 30 40 50 60 70 80 90 100 Ur S1 normal load kPa S1 = strength available S2 = strength required b. Only a modest increase in pore pressure is Ur = suction required to maintain slope stability required to lower the mobilized shear strength to the resistance envelope (material properties, a (σ - Uw) c' = 10 kPa, Φ' = 25 kPa). Source: Anderson, Kemp, and Shen 1987. Source: Anderson, Kemp, and Shen 1987. CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 1 7 RESISTANCE ENVELOPE METHOD USAGE To determine whether negative pore pressures are required to maintain slope stability SOURCE Resistance envelope calculation in Anderson et al. (1997) FURTHER See section 5.6.4 DISCUSSION F IG U R E 3. 34  Inadequate retaining wall unlikely to provide an effective landslide risk design reduction measure. The essential general sta- bility requirements for such structures would appear to be drainage to ensure the mainte- nance of unsaturated conditions behind the wall, and an avoidance of surcharging the slope immediately behind the wall. In reality, these two conditions are not likely to be met in such communities with unauthorized hous- ing. Alternative retaining wall designs incor- porating features to counteract overturning failure, such as wall backtilt and an extended a. Typical failure of modest retaining wall built wall toe, would also seem impractical in this by resident. context, given their increased costs over sim- ple walls and the greater construction control required to ensure structural integrity. Summary: landslide hazard assessment methods • Review slope stability software available either locally or online. • Use the resistance envelope method for assessing the role of negative pore pres- sures, only if there is adequate technical b. Retaining wall built by resident failed, with support for the analysis and interpretation lower part of wall displaced to rear of property. and if circumstances warrant that discrimi- nation. • Use retaining wall analysis software to gen- dient, are such structures effective? Given the erate local case studies to affirm the type of number of such retaining wall failures, it is structures that would be needed to enhance important to assess the stability of a typical slope stability. Assess whether such struc- structure so clearer guidance can be given to tures would be affordable and desirable at community residents. the community scale. For this purpose, a standard static hydrol- ogy retaining wall stability analysis can be undertaken (see, e.g., BSI 1994; Craig 1997; and MILESTONE 3: USACE 1989). The findings of such an analy- Presentation made to MoSSaiC sis, outlined in section 3.7.5, suggest that sim- teams on landslide processes and ple single-skin structures of the type com- monly constructed by residents are unlikely to slope stability software meet the stability criteria—and are equally 1 1 8    C H A P T E R 3 .   U N D E R S TA N D I N G L A N D S L I D E H A Z A R D 3.7 RESOURCES 3.7.1 Who does what CHAPTER TEAM RESPONSIBILITY ACTIONS AND HELPFUL HINTS SECTION Know the types of landslides • Become familiar with the specific types of landslides that 3.3 addressed by MoSSaiC MoSSaiC seeks to address Funders and policy makers Coordinate with the MCU for any technical information required Understand the types of • Become familiar with the specific types of landslides that 3.3 landslides addressed by MoSSaiC MoSSaiC seeks to address Understand the factors that 3.4; 3.5 determine slope stability and the MCU associated assessment methods Coordinate with government task team for any technical information required Understand the types of • Become familiar with the specific types of landslides that 3.3 landslides addressed by MoSSaiC MoSSaiC seeks to address • Look at this chapter, field sites, and local reports of 3.4; 3.5 Understand the factors that landslides to appreciate all the possible triggering determine slope stability and the mechanisms associated assessment methods Helpful hint: Undertake site visits to landslide sites and identify types and potential localized causes. Be familiar with, and select • Review relevant slope stability assessment methods with 3.6 appropriate, scientific methods respect to software, expertise, and data likely to be for assessing local landslide locally available Government task hazards teams Brief the MCU and all task teams • Landslide assessment and engineering task team should Whole on (1) the scope of MoSSaiC with prepare and deliver presentation chapter respect to local landslide types; (2) landslide preparatory, aggravating, and triggering factors; and (3) the scientific basis for assessing slope stability, especially with respect to locally available expertise and software Coordinate with community task teams when appointed Community task • Look at this chapter, visit field sites (this is especially 3.5 When appointed, understand the teams important), and review local reports of landslides to variables that affect slope appreciate all the possible preparatory, aggravating, and stability triggering mechanisms Coordinate with government task teams CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 1 9 3.7.2 Chapter checklist SIGN- CHAPTER CHECK THAT: TEAM PERSON OFF SECTION 99Knowledge has been acquired of the subset of landslide types that MoSSaiC 3.3 seeks to address 99Knowledge has been acquired of relevant slope stability processes 3.4; 3.5 99Site visits to known and potential landslide sites to examine potential triggering mechanisms and suitability for MoSSaiC approach have been 3.3; 3.4; 3.5 undertaken 99Potential scientific tools for assessing landslide hazard have been examined 3.6 99Milestone 3: Presentation made to MoSSaiC teams on landslide processes and slope stability software 99All necessary safeguards complied with 1.5.3; 2.3.2 3.7.3 Rainfall thresholds for triggering θi = unsaturated moisture content (m3 m−3) landslides θs = saturated moisture content (m3 m−3) ψi = suction value at moisture content θi (m) The website developed by the Italian Istituto m = number of equal increments of θ from di Ricerca per la Protezione Idrogeologica θ = 0 to θ = θs (IRPI) contains a comprehensive worldwide j,i = summation indexes listing of rainfall threshold triggering relation- Mohr-Coulomb equation (Coulomb 1776) ships (http://wwwdb.gndci.cnr.it/php2/rain- fall_thresholds/thresholds_all.php?lingua=it). s = c' + ( σ − u ) tan φ' 3.7.4 CHASM principle equation set s = soil shear strength (kPa) The following equation sets are from Wilkin- c' = effective soil cohesion (kPa) son et al. (2002). See table 3.9. Φ' = effective angle of internal friction (degrees) σ = total normal stress (kPa) Richards’ equation (Richards 1931) u = pore water pressure (kPa) ∂θ ∂  ∂θ  ∂Κ Bishop stability equations (Bishop 1955) =− D  − ∂t ∂ z  ∂ z  dz ∑ ( c'l + ( P − ul ) tan φ' ) n θ = volumetric moisture content (m3 m−3) FS = i=0 ∑ W tan α n t = time (s) i=0 z = vertical depth (m) D = hydraulic diffusivity (m2 s−1) where Millington-Quirk equation (Millington and Quirk  1  P = W − ( c'l sin α − ul tan φ' sin α ) / mα 1959)  FS 0  m ∑ (( 2 j + 1 − 2i ) ψ ) j −2 and K i = K s (θ i / θ s ) p j =i m  tan φ'  ∑ (( 2 j − 1) ψ )j −2 mα = cos α  1 + tan α  FS0   j =1 p = pore interaction term Ki = unsaturated conductivity (m s−1) n = number of slices Ks = saturated conductivity (m s−1) 1 2 0    C H A P T E R 3 .   U N D E R S TA N D I N G L A N D S L I D E H A Z A R D TAB L E 3 .9  Units for the parameters used in CHASM PARAMETER GROUP PARAMETER NAME SYMBOL/UNIT Slope height H (m) Feature geometry Slope angle α (degrees) Slope plan convergence/divergence radius C (m) Mesh resolution (width, depth, breadth) a w, d, b (m) Numerical Iteration period a t (s) Rainfall p (m s−1) Saturated hydraulic conductivity Ks (m s−1) Hydrological Initial surface suctionb ψt0 (m) Initial water table height b wt (% slope height) Suction-moisture curve ψ (m) –θ (m3 m−3) Effective angle of internal friction Φ' (degrees) Geotechnical Unsaturated/saturated bulk density γus, γs (kN m−3) Effective cohesion c' (kN m−2) Root tensile strength Ï„r (kN m−2) Vegetation cover/spacing vc (%), vs (m) Leaf area index lai (m2 m−2) Aerodynamic resistancec ra (s m−1) Vegetation Canopy resistancec rc (s m−1) Canopy/trunk storage capacity cs, ts (m) Root depth/lateral extent Rd, Rl (m) Vegetation surcharge Sw (kN m−2) Net radiation Rn (W m−2) Atmosphericc Relative humidity Rh (%) Temperature T (0C) a. Determined according to Beven (1985) to maintain numerical stability in Richards’ equation. b. Initial surface suction and water table heights (defined as percentage of slope height measured to the toe of the slope) are assigned according to measured field conditions or hypothetical scenario. Richards’ equation is then iterated until steady-state conditions are attained or the required soil moisture conditions are reached. c. Atmospheric variables and canopy/aerodynamic resistance are required if the user wishes to determine soil evaporation and evapotranspiration using the Penman-Monteith equation. In the absence of this information, a sinusoidal function is used with the maximum evaporation rate defined at midday The sinusoidal function operates between 0600 and 1800 hours. During the remaining time, the respective evaporation rate is set to 1/100th of the midday maximum. Penman-Monteith equation (Monteith 1973) FS = factor of safety c' = effective soil cohesion (kPa) Rn + Ï?c pVPD / ra l = slice length (m) Ep = Δ+γ (1 + rc / ra) λ   α = slice angle (degrees) u = pore water pressure (kPa) Ep = potential evapotranspiration rate (m s−1) Φ' = effective angle of internal friction (degrees) ra = aerodynamic resistance (s m−1) W = weight of the soil (kPa) rc = canopy resistance (s m−1) Δ = slope of the saturation vapor pressure— temperature curve (kg m−3 K−1) CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 2 1 λ = latent heat of vaporization of water wall, groundwater included as a specified hor- (≈ 2.47 × 106 J kg−1) izontal water table position, unsaturated earth Ï? = density of air (≈ 1.2 kg m−1) pressures acting above the saturated ground- γ = psychrometric constant (γ ≈ 66 Pa K−1) water level, and saturated earth pressures and VPD = vapor pressure deficit (kg m−1 s−2) direct hydrostatic pore water pressures acting cp = specific heat of air (J kg−1 K−1) below. Details of the specific methodology Rn = net radiation (W m−2) may be found in Blake (2003). No uplift water force on the base of the wall Root reinforcement equation (Wu, McKinnell, or at the front of the wall was considered. The and Swanston 1979; Wu 1995) active earth pressure was calculated using the Δc' = c'R = tR(cosθ tanΦ + sinθ) Coulomb coefficient method. Factors of safety c' = effective cohesion (kPa) against sliding, overturning, and bearing-limit- c'R = effective cohesion attributed to the root state retaining wall stability failure modes network (kPa) were determined. θ = angle of shear rotation (degrees) Earth pressures in front of retaining walls Φ = angle of internal friction (degrees) and the possibility of tension cracks in the tR = average tensile strength of the roots per retained material both need to be considered. unit area of soil (kPa) No passive earth pressures acting in front of the wall were included in this analysis, which 3.7.5 Static hydrology retaining wall is a common conservative assumption. In real- stability analysis ity, the wall stability will be increased slightly The following describes a simple retaining by this force although it cannot be relied upon wall stability analysis by Anderson et al. (2011). due to unplanned excavations in front of the A simple wall geometry was defined (fig- wall. Tension cracks resulting from the ure  3.35) with the following specifications: retained material cohesive properties were active earth pressure acting on the back of the included in the analysis, with their depth cal- culated using the method given in Craig (1997). Their effect is to reduce the stability benefits FI G U R E 3 . 3 5  A simple retaining wall geometry used for the of the cohesive element of the retained mate- retaining wall analysis rial. Similarly, no account was taken of any surface water filling these cracks and exerting detri- tension mental additional hydrostatic pressure on the cracks wall. Cohesion reduces the horizontal compo- 0.3m 0m 25Ëš overturning nent of the total active earth pressure on the failure mode back of the wall (a stabilizing effect) while also 0.3m unsaturated earth resulting in adhesion between the wall and the water- pressures (above retained material. Thus, the effect of cohesion 0.6m table water table) 1.5m is to reduce the effectiveness of the wall weight depth 0.9m vertical wall (a destabilizing effect). scenarios Using these specifications, an analysis was 1.2m saturated earth undertaken for the following horizontal water pressures and table depths (with hydrostatic pore water 1.5m direct hydrostatic pore pressures pressure distribution) below the ground sur- (below water sliding failure face: 1.50 m (at base of wall—fully unsaturated mode table) retained material), 1.20 m, 0.90 m, 0.60 m, bearing failure mode 0.30 m, 0.00 m (at top of wall—fully saturated retained material). Source: Anderson et al. 2011. The stability analysis parameters and results are given in table 3.10. The results show 1 2 2    C H A P T E R 3 .   U N D E R S TA N D I N G L A N D S L I D E H A Z A R D TAB L E 3 .10  Results of an illustrative standard static hydrology retaining wall stability analysis WATER TABLE NO SURCHARGE 10 kN m−2 SURCHARGE DEPTH BELOW Overturning Sliding Bearing Overturning Sliding Bearing SURFACE (m) failure failurea failure failure failure failure 1.50 1.79 −1.74 4.47 0.22 0.55 0.58 1.20 1.72 −1.90 4.38 0.22 0.54 0.58 0.90 1.39 −2.65 3.89 0.21 0.50 0.57 0.60 0.90 −8.13 3.00 0.20 0.44 0.55 0.30 0.51 4.03 2.09 0.17 0.38 0.51 0.00 0.28 1.33 1.40 0.15 0.32 0.45 Source: Anderson et al. 2011. a. In the factor of safety calculation, while negative values are possible, such solutions have no physical meaning. Note: Parameter values used for the analysis: Wall unit weight: 23 kN m−3 (concrete blocks) Retained material unsaturated unit weight: 15 kN m−3 Retained material saturated unit weight: 19 kN m−3 Effective cohesion: 10 kPa Wall adhesion: 5 kPa (standard assumption of cohesion ÷2) Effective angle of internal friction (Φ): 25° Wall-backfill friction angle: 13° (standard assumption of Φ ÷2) Wall-foundation friction angle: 17° (standard assumption of 2 × Φ ÷3) Foundation bearing capacity: 400 kN m−2 Surcharge: 0 or 10 kN m−2 (it is usual to have a conservative assumption of 10 kN m−2 minimum to provide a margin of safety against unplanned loads, vehicle movement, etc.) that if there is a modest (10 kN m−2) surcharge, tion enhanced material shear strength is not the wall will be unstable for all failure modes accounted for. However, this is not considered and water table scenarios. Comparison with material to the broad conclusions given in the Hong Kong SAR, China, Geotechnical table 3.10. Control Office (GCO 1984) critical stability threshold factor of safety values (overturning: 3.7.6 References 1.50, sliding: 1.25, bearing: 3.00) shows that the Aleotti, P., and R. Chowdhury. 1999. “Landslide wall will meet these design thresholds provid- Hazard Assessment: Summary Review and New Perspectives.â€? Bulletin of Engineering Geology ing the material behind the wall remains and the Environment 58: 21–44. unsaturated. The overturning failure mode is critical, an observation in agreement with field Anderson, M. G., A. J. C. Collison, J. Hartshorne, D. M. Lloyd, and A. Park. 1996. “Developments evidence of overtilted retaining walls. This is in Slope Hydrology—Stability Modelling for explained partly by the fact that (beneficial) Tropical Slopes.â€? In Advances in Hillslope soil cohesion has a smaller effect on the wall Processes, ed. M. G. Anderson and S. M. overturning moment, since tension cracks Brooks, 799–821. 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CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 2 7 “How can we encourage developing countries to invest more in disaster risk reduction? We need to help governments make the choices of where to invest.â€? —Department for International Development, “Frequently Asked Questions on Disaster Risk Reductionâ€? (2006) CHAPTER 4 Selecting Communities 4.1 KEY CHAPTER ELEMENTS 4.1.1 Coverage This chapter outlines the process for identify- (Management of Slope Stability in Communi- ing the communities most at risk from land- ties) projects. The listed groups should read slides so they can be prioritized for MoSSaiC the indicated chapter sections. AUDIENCE CHAPTER F M G C LEARNING SECTION    Principles for comparing landslide risk at various locations; data and expertise 4.1, 4.2, 4.3 required; how to design an appropriate community prioritization process   How to compare landslide susceptibility or hazard at multiple locations 4.4    How to compare the vulnerability of exposed communities 4.5   How to create a prioritized list of at-risk communities 4.6  How to create a base map for each selected community 4.7 F = funders and policy makers  M = MoSSaiC core unit: government project managers and experts  G = government task teams: experts and practitioners  C = community task teams: residents, leaders, contractors 4.1.2 Documents CHAPTER DOCUMENT TO BE PRODUCED SECTION Report on decision-making process, roles, and responsibilities for community selection 4.1, 4.2, 4.3 Report on outcomes of landslide susceptibility/hazard assessment and vulnerability assessment 4.4, 4.5, 4.6 concluding with a prioritized list of communities for engagement in MoSSaiC project Base maps for the selected communities 4.7 129 4.1.3 Steps and outputs STEP OUTPUT 1. Define the community selection process Agreed-upon • Identify available experts in government selection method • Determine availability of software and data and criteria, roles • Request permission to use data if necessary and responsibilities, • Design appropriate method for selecting communities timeline 2. Assess landslide hazard List or map of • Data acquisition: topography, soils, geology, land use, past landslides relative landslide • Data analysis: landslide susceptibility or hazard within the study area susceptibility of different areas 3. Assess exposure and vulnerability List or map of • Data acquisition: community locations, building footprints, housing/popula- relative tion density, census data or poverty data vulnerability of exposed • Data analysis: vulnerability of exposed communities to landslide impacts in communities terms of physical damage, poverty, or other criteria 4. Assess landslide risk List or map plus list • Data analysis: landslide susceptibility/hazard, exposure, and vulnerability data of most-at-risk combined to determine overall landslide risk for study area communities for possible risk • Data analysis: identify communities exposed to highest levels of landslide risk reduction measures 5. Select communities Prioritized • Conduct brief site visits of short-listed communities to confirm results community short list • Consult community liaison task team and other relevant local stakeholders to review list • Confirm prioritized community short list according to selection criteria 6. Prepare site map information for selected communities Hard-copy map • Data acquisition: most detailed maps and aerial photos of selected communities and aerial photo • Map preparation: assemble community maps/photos and print hard copies for use on site 4.1.4 Community-based aspects munities for implementation of landslide haz- ard reduction measures using MoSSaiC. This A critical part of the selection process is for community selection process identifies government task teams to visit short-listed (1) areas where slopes are susceptible to land- communities to confirm the likely landslide slides, (2) the exposure and vulnerability of risk and the suitability of a MoSSaiC project. communities to these potential landslide Community representatives can provide infor- events, (3) the overall landslide risk, and mation on local landslide history, socio- (4) the suitability of a MoSSaiC project for at- economic vulnerability, and community per- risk communities. ceptions of the risk; they should be consulted The sophistication of the methods used will during these visits. depend on local data and software availability, and the level of expertise of the government task teams. Outputs could range from a simple 4.2 GETTING STARTED prioritized list of communities to a detailed landslide risk map for a region or country. A 4.2.1 Briefing note variety of different approaches might be adopted in performing this task. Whatever The aim of this chapter is to provide a frame- method is used, community selection should work for developing a prioritized list of com- be justifiable in terms of the scientific ratio- 1 3 0    C H A P T E R 4 .   S E L E C T I N G CO M M U N I T I E S nale underpinning the landslide risk assess- spatially distributed analysis of risk over wide ment. areas). Once the communities have been selected, The MCU should oversee the development the mapping task team assembles the most- of the method for community selection and be detailed maps available for these communi- responsible for deciding the final list of prior- ties. These maps form the basis for the com- ity communities. A lead investigator should be munity-based landslide hazard and drainage selected to coordinate the multidisciplinary mapping exercise (described in chapter 5) and process of data acquisition and analysis. Dif- subsequent implementation of appropriate ferent task teams should work together to hazard reduction measures. combine their understanding of slope pro- cesses and landslide hazard, technical exper- Why a community selection process is needed tise in data management and/or GIS mapping, The aim of a MoSSaiC intervention is to reduce and experience in vulnerability or poverty landslide hazard in the most vulnerable com- assessment. munities. In any country or region, there may be 4.2.2 Guiding principles many communities at risk, and government The following guiding principles apply in awareness of these communities will vary. The selecting communities for MoSSaiC project MoSSaiC core unit (MCU) should agree on a interventions: process by which communities are selected for • Be realistic about the data, time, and exper- this type of landslide risk reduction project. tise available for the community selection Having a structured approach to commu- process. It is better to design a simple, low- nity selection also ensures that community tech, but achievable decision-making pro- inclusion, exclusion, and prioritization can be cess than to attempt to use software and justified to the communities, the government, techniques for which there is insufficient and donor agencies. Therefore, the selection expertise or poor quality data. process should make use of any relevant quan- titative data relating to landslide susceptibil- • The community selection process should ity/hazard and community vulnerability. It be transparent, regardless of the quality of should also be able to incorporate qualitative the data or the sophistication of the land- data such as local knowledge, reports from slide hazard and vulnerability assessment communities, and information from govern- methods, so that priorities and decisions ment ministries (such as public works, social can be justified to all stakeholders. This development, and emergency management). transparency assists in explaining decisions to residents in communities that may sub- Key activities, resources, and teams sequently not be selected, avoiding bias The community selection process primarily toward particular individuals or agendas in involves data acquisition and analysis. Data decision making, and enabling the project may be in the form of maps and lists of known to be more easily audited and evaluated. or suspected landslides; digital maps of land use, topography, drainage, soil, and geology; 4.2.3 Risks and challenges and data relating to vulnerability (such as cen- sus data at enumeration district level or bet- Limited available data ter). Depending on the scope of the study and the available data and expertise, the analysis The community selection process requires the may be carried out using spreadsheet or data- comparison of the landslide risk affecting mul- base software (to compile and compare data tiple communities. This may be done as a on a list of communities), or a geographic search for at-risk communities over a wide information system (GIS) (for mapping and area (with no prior knowledge of which com- CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 3 1 munities may be identified), or may involve slide initiation; hazard maps additionally comparing known at-risk communities. Both convey the temporal probability of land- approaches require data—the type, quality, slide initiation. and availability of which will determine the community selection method used. Test the provenance and utility of other Whatever data are used in the community types of data, such as community vulnerability selection process, be transparent about their information, in a similar manner before source and quality when presenting results to including it in the risk analysis. decision makers and communities. 4.2.4 Adapting the chapter blueprint to Interpreting landslide hazard maps existing capacity When using preexisting landslide hazard Use the matrix opposite below to determine maps be aware how they were generated the availability of physical data (relating to because this affects how they should be inter- landslides), vulnerability data, software, and preted. the expertise of the government team. As described in chapter 3, several different 1. Assign a capacity score from 1 to 3 (low to factors can act together to cause landslides. high) to reflect existing capacity for each These factors can vary over very short dis- element in the matrix’s left-hand column. tances and also over time. The best landslide hazard maps are based on a combination of 2. Identify the most common capacity score as accurate, high-resolution digital maps of these an indicator of the overall capacity level. factors and records of past landslides. Devel- 3. Adapt the blueprint in this chapter in accor- oping such maps requires a good understand- dance with the overall capacity level (see ing of the processes that cause landslides and guide at the bottom of the opposite page). experience in using GIS and spatial data sets. A landslide hazard map based on inaccurate, incomplete, or low-resolution data, or on faulty scientific assumptions, can be mislead- 4.3 DEFINING THE COMMUNITY ing. SELECTION PROCESS Assess the provenance and utility of preex- isting landslide hazard maps in terms of the The community selection process comprises following: two integrated methods—a landslide risk assessment at multiple locations and the appli- • The data used to compile the map, and its cation of decision-making criteria for selecting quality and resolution—These data can communities. The selection process will be include environmental (preparatory) fac- constrained by the technical capacity for land- tors, triggering factors, and past landslides slide risk assessment and the scope of the proj- • The type of landslide represented— ect as defined by funders and government. MoSSaiC is directed toward rotational and For a given technical capacity and project translational slides in weathered materials scope, use the guidance in this section to iden- tify the following: • The expertise of the map maker and the method used—Methods include direct • A suitable approach to comparing levels of landslide mapping, semi-quantitative index landslide risk at multiple locations overlay methods, and spatially distributed • The criteria for community selection modeling of slope factor of safety • The data requirements for the community • The slope stability information conveyed by selection process the map—Landslide susceptibility maps show the relative spatial likelihood of land- • The roles of the MCU and task teams 1 32    C H A P T E R 4 .   S E L E C T I N G CO M M U N I T I E S EXISTING CAPACITY CAPACITY ELEMENT 1 = LOW 2 = MODERATE 3 = HIGH Local geotechnical expertise No local geotechnical experts Geotechnical engineers or Geotechnical engineers or and no local knowledge of academics with some academics with expertise in landslide processes or hazard experience of landslide hazard landslide hazard assessment in assessment assessment in the field or in the field and in using GIS using GIS Digital map availability No digital maps Some digital maps available or High-resolution digital maps at low resolution available Preexisting landslide suscepti- No (or poor quality) landslide Relevant landslide susceptibil- Good quality, high-resolution, bility, hazard, or risk maps susceptibility/hazard maps ity map available, sufficient relevant landslide susceptibil- resolution and quality ity/hazard map available GIS software expertise No software or trained staff GIS software available and GIS software and experienced experience with simple GIS staff analysis Landslide records No landslide records Some landslide records kept Comprehensive, geo-refer- separately by different enced landslide records agencies in different formats integrated and accessible for different purposes across multiple agencies Vulnerability data availability No data on community Data on proxies for vulnerabil- Vulnerability assessment vulnerability ity (e.g., census data for methods and data established calculating poverty indicators) Project safeguards Documented safeguards need Documents exist for some Documented safeguards to be located; no previous safeguards available from all relevant experience in interpreting and agencies operating safeguard policies CAPACITY LEVEL HOW TO ADAPT THE BLUEPRINT 1: Use this chapter Unless outside GIS expertise and data can be obtained, the community selection process should be based in depth and as a on reports and local knowledge (word of mouth) of landslide-prone areas and vulnerable communities. The catalyst to secure output will be a refined list of communities based on qualitative information sources only. The MCU needs support from to strengthen its capacity for community selection; this might involve the following: other agencies as • Using this book/chapter to gain an understanding of types of available community selection methods appropriate • Identifying colleagues in government or higher education with knowledge of landslides and community vulnerability assessment and considering their appointment as the lead investigator in the community selection process • Working with local commercial or higher education partners to access digital maps or GIS expertise 2: Some elements It might be possible to use GIS data to indicate relative risk across a wide area; this can be refined with local of this chapter knowledge. The expected output at this level will be a low-resolution risk map and a list of priority will reflect current communities. The MCU has strength in some areas, but not all. Elements that are perceived to be Level 1 practice; read the need to be addressed as above. Elements that are Level 2 will need to be strengthened, such as the remaining following: elements in depth • Receiving assistance or training in the use and application of GIS software and use them to further strengthen • Integrating such data and knowledge across ministries capacity 3: Use this chapter The MCU can likely produce and implement community selection using existing capacity. Detailed GIS- as a checklist based landslide risk mapping is possible without any additional training and can be refined with data on past landslides. The expected output will be a high-resolution landslide risk map and a community short list verified through field visits. The following would nonetheless be good practice: • Document the community selection methodology for future reference • Establish a landslide risk database and risk management planning tool CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   1 33 4.3.1 Approaches to comparing levels of causal factors and identifying zones of rela- landslide risk at multiple locations tive landslide susceptibility • Probabilistic methods (based on landslide The community selection process is founded inventories) for determining the likelihood on data acquisition and analysis involving a of landslide occurrence derived from previ- combination of fieldwork and computer-based ous events work to obtain a relative ranking of landslide risk. The aim is to undertake an appropriate • Bivariate and multivariate statistical form of landslide risk assessment to identify approaches (also requiring historical land- the communities with the highest risk. Two slide data) for indirectly identifying land- possible approaches to this risk assessment slide causal factors task are introduced below. The exact form the • Deterministic spatially distributed mod- landslide risk assessment will take depends on eling of physical slope stability processes local capacity and data. Sections 4.4–4.6 pro- (this is not the same as using site-specific vide greater information on the specific land- models such as CHASM [Combined Hydrol- slide hazard, vulnerability, and risk assessment ogy and Slope Stability Model], section 3.6). methods associated with these two approaches. GIS may also be used to determine the Field reconnaissance and risk ranking exposure of different elements (people, A low-tech approach to landslide risk compari- houses, public buildings, utilities, etc.) to the son among communities is to undertake a landslide hazard and to assess the physical, qualitative assessment of the relative hazard economic, and social vulnerability of these ele- and vulnerability of an existing list of commu- ments. Sources of information on exposure nities using rapid field reconnaissance meth- and vulnerability include land-use maps, maps ods. This approach entails having a team of of land and asset values, and geo-referenced landslide experts, engineers, or geotechnicians, census data containing socioeconomic infor- and vulnerability assessment experts visit each mation. community on the list. This team describes Table 4.1 indicates the main types of spa- landslide hazard, exposure, vulnerability, and tially distributed data that may be used to risk in relative terms or by using a numerical assess and map landslide risk at different spa- scoring system. An inventory of hazardous tial scales—from information on past land- slopes is thus established, and the relative land- slides, to environmental and triggering factors, slide risk to communities can be ranked. to data relating to elements at risk. In many cases, comprehensive data on past landslides Digital data and GIS analysis may not be available or may relate to types of landslide hazard not relevant to MoSSaiC A more technically demanding approach (such as rock falls or debris flows). Similarly, involves using digital spatial data and GIS. not all the environmental and triggering fac- This approach can be useful when there are tors and elements at risk in this table will nec- too many communities for field reconnais- essarily be applicable (such as lithology, seis- sance to be practical, and/or where is little mic data, and transportation network maps). prior knowledge about which communities If hazard, exposure, vulnerability, and risk are affected by landslides. If the digital spatial mapping exercises have been previously data are of sufficient quality, large areas can be undertaken as part of another study or project, assessed using this approach. it may be appropriate to incorporate such There are four main classes of GIS-based maps into the community selection process. landslide hazard assessment: Review these maps to confirm that they have a • Heuristic (expert-based) methods for com- sound basis and take into account the land- bining digital maps of potential landslide slide hazard types relevant to MoSSaiC. 1 3 4    C H A P T E R 4 .   S E L E C T I N G CO M M U N I T I E S TAB L E 4.1  Schematic representation of the basic data sets for landslide susceptibility, hazard, and risk assessment RISK IDEAL UPDATE DATA SCALEb HAZARD MODELc METHODd FREQUENCY (YEARS) Main type Layer 10......1......0.002(DAY) RSa S M L D H S D P S Q Landslide inventory Landslide Landslide activity inventory Landslide monitoring Requires results of heuristic, statistical, or deterministic hazard analysis Digital elevation model Slope angle/aspects, etc. Requires results of probabilistic hazard analysis Internal relief Flow accumulation Lithology Structure Environmental Faults factors Soil types Soil depth Slope hydrology Main geomorphology units Detailed geomorphology units Land-use types Land-use changes Rainfall Triggering Temperature/evapotranspiration factors Earthquake catalogues Ground acceleration Buildings Transportation networks Lifelines Elements at Essential facilities risk Population data Agriculture data Economic data Ecological data Source: van Westen, Castellanos Abella, and Sekhar 2008. Note: ï?® = critical; ï?® = highly important; ï?® = moderately important; ï?® = less important; ï?® = not relevant. a. Usefulness of remote sensing for acquisition of data. b. Importance of the data layer at small (S), medium (M), large (L), or detailed (D) scales, related to feasibility of obtaining data at that particular site. c. Importance of the data set for heuristic (H), statistical (S), deterministic (D), or probablistic (P) models. d. Importance of the data layer for (semi-)quantitative (S) or qualitative (Q) vulnerability and risk analysis. Choosing a risk comparison approach more detailed descriptions of specific meth- ods and data requirements. The chosen Be pragmatic when deciding which approach method should be to use for analyzing and comparing land- slide risk among communities. Use this sec- • not overly ambitious—requiring skills, tion to identify the general data require- software, data, and time far beyond the ments for different approaches to landslide reasonable capacity of the government risk assessment. Sections 4.4–4.6 provide task teams; CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 3 5 • designed to provide enough information for If there is no regular use of wide-area data the purpose of the project, but not necessar- for landslide risk mapping, or if there is already ily a comprehensive quantitative analysis a long list of communities requesting help, of risk—in many cases, decision makers will then a bottom-up or list-driven approach may simply need a screening process for identi- be appropriate. This approach could be vul- fying and prioritizing communities; and nerable to political agendas to include certain communities on the list. On the other hand, • rigorous, in that, regardless of the govern- experienced users of wide-area digital maps ment’s technical capacity, there should be a and GIS software might formulate questions transparent method for community selec- in a top-down manner to derive a list of com- tion that provides the basis for justifying munities. Such an approach is perhaps more selections. politically objective, but requires considerable technical expertise and a good data set. In real- 4.3.2 Methods for community selection ity, a combination of the two methods may be To create an integrated community selection used to confirm the communities on the list. process, combine the chosen landslide risk • Example 1: A priori list-driven questions assessment approach with project-specific for bottom-up selection criteria for selecting communities. When choosing the landslide risk assess- 1. Where have landslides already occurred? ment approach and defining the community 2. How many houses are exposed, and is selection criteria, take the following influences housing density moderate to high? into account: 3. Are the exposed households physically • Obligations under the funding loan or grant and socioeconomically vulnerable? contracts to work in specific locations or meet certain criteria and safeguards 4. Based on the above, which communities are at greatest risk from landslides? • Community-driven demands for solutions to landslide issues 5. Would an intervention be cost-effective, and does it fit the project scope? • Scientific/technical interest in using cer- tain risk assessment methods • Example 2: GIS-based approach for wide- • Awareness and availability (or lack thereof ) area or top-down selection of digital data, GIS, or mapping methods 1. Where are the areas with the highest • Political agendas landslide susceptibility or hazard? Selection criteria 2. Within these landslide areas, where are the most-exposed communities? Begin by defining the questions that, when 3. Within these exposed communities, answered, will become the selection criteria. where is the greatest physical and socio- Each country will ask these questions and economic vulnerability? define their criteria differently depending on their expertise, priorities, and approach to 4. Based on the above, which communities the task. However, two broad criteria for are at greatest risk from landslides? community selection should always be met: 5. Where would an intervention be most the high level of landslide risk to a commu- cost-effective and appropriate? nity (hazard, exposure, and vulnerability) relative to other communities, and the appro- Figure 4.1 illustrates how these two types of priateness of MoSSaiC as a means of address- approach may be used individually or in con- ing that risk. junction. 1 3 6    C H A P T E R 4 .   S E L E C T I N G CO M M U N I T I E S FI G U R E 4.1  Top-down and bottom-up community selection methods Assessment Method: Top-down national search Method: Bottom-up local search criteria (wide area/GIS based) (list driven/reconnaisance based) Hazard Map of landslide susceptibility or Question: Where have landslides hazard zonation based on already occurred? • slope angle • Known landslides • soil types • Areas of slope instability • drainage density • Suspected future landslides • topography • Occurring during or after rain • previous rotational/translational • In soils not rock rainfall-triggered landslides • Rotational or translational Exposure Map of locations of houses and Question: How many houses are density of settlements showing affected, and is housing density • house locations or footprints moderate to high? • housing density and clustering • More than 10 houses in potential (footprint area of houses as a landslide area proportion of the ground • Houses clustered in potential surface) landslide area (housing density • population density comprising > 30% land cover) Vulnerability Map of socioeconomic Question: Are the affected vulnerability showing households low income? • settlement type (authorized, • Wooden or small concrete unauthorized, squatter) houses on small plots • building type (concrete/ • Lack of infrastructure (metaled wooden, high/low rise, etc.) paths/roads, drainage, lighting, • poverty (indicators, proxies) etc.) • High unemployment Landslide risk Create national list and refine Confirm top-down search and/or to communities using bottom-up local search create community short list MoSSaiC interventions involve the con- Regardless of the precise wording of the struction of strategically aligned networks of selection criteria, the aim should be to assess surface water drains. Thus, the greater the landslide susceptibility/hazard, the exposure housing density within the drainage network and vulnerability of communities to that haz- area, the greater the cost-effectiveness will be ard, the overall landslide risk, and the appro- in terms of the number of households benefit- priateness of MoSSaiC. Project-specific crite- ing from the intervention. To estimate the ria may be used to refine and prioritize the cost-effectiveness of a MoSSaiC intervention, community short list. take into account the number and density of Data sources and methods of analysis houses exposed to the landslide hazard as well as the potential damage and costs that could be Once the general landslide risk assessment avoided by reducing the likelihood of landslide approach and community selection criteria occurrence. Other cost factors to take into have been identified, consider the specific account might relate to the potential cost of sources of information that could help answer construction at that location (determined by these questions. Confirm how the information factors such as transportation of materials and will be analyzed—whether by simple qualita- ease of excavating slope material). tive field reconnaissance methods for ranking CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   1 37 or scoring landslide risk in communities or data, the more comprehensive the landslide with qualitative, semi-quantitative, or quanti- risk assessment will be. However, it is not tative methods using digital maps and GIS expected or required that every country have software. the complete suite of data listed here. Table 4.2 provides a wide-ranging, although Agreeing on the community selection process not exhaustive, list of potential data and analy- sis methods. Generally, the more data sources Each step in the community selection process and the better the quality and analysis of the should be defined and agreed upon by the TAB L E 4.2  Framework of potential data and analysis methods FORMAT POSSIBLE ANALYSIS METHOD INFORMATION SOURCE (LIST/HEURISTIC TO DIGITAL MAP) (QUALITATIVE TO QUANTITATIVE) Prior list of communities requesting assistance Residents reporting problems to List Qualitative assessment government Government ministers or agencies List Qualitative assessment reporting problems Landslide susceptibility and hazard assessment List Qualitative assessment Hard-copy map/aerial photos Qualitative assessment Records of previous landslide locations Digital map Incorporate within GIS-based qualitative or semi-quantitative landslide susceptibility or hazard analysis Local expert knowledge Qualitative assessment Wide-area landslide preparatory Hard-copy map Qualitative assessment factors (slope angles, soil types, land Digital map GIS-based: landslide susceptibility analysis use, drainage, etc.) GIS plus infinite slope model: quantitative hazard analysis Expert observations Expert-based qualitative or semi-quantita- Site-specific slope data and landslide tive hazard assessment expert or engineera Physical parameters Physics-based modeling (quantitative) Exposure and vulnerability assessment Site visits by community officer and Qualitative assessment Exposure: housing type and density engineera information Aerial photos and land-use maps Qualitative assessment Landownership maps Semi-quantitative assessment Site visits by engineera Qualitative assessment Physical vulnerability of elements at Records of previous damage Semi-quantitative assessment risk to damage by landslide Value of elements at risk Quantitative assessment Site visit by social scientist or community Qualitative assessment officera Census data Semi-quantitative or quantitative assess- ment of poverty Socioeconomic vulnerability Geo-referenced census data GIS-based semi-quantitative or quantita- tive assessment of poverty Poverty survey Various methods Geo-referenced poverty survey Map directly in GIS a. These data may be collected in the field as part of the community short list review or to confirm a wider landslide risk assessment. 1 3 8    C H A P T E R 4 .   S E L E C T I N G CO M M U N I T I E S MCU. The timeline, roles, and responsibilities indicate areas of relative landslide for undertaking the analysis should then be susceptibility, exposure, vulnera- set. bility, and risk (undertaken by GIS For the examples given above, the main technicians and engineers/geo- steps in the community selection process technicians) or could be defined as follows. b. Using advanced quantitative GIS • Example 1: A priori list-driven process for map analysis in conjunction with bottom-up selection spatially distributed numerical slope stability models to quantify —— Main data format: Soft data comprising landslide hazard, exposure, vul- lists of known landslide hotspots and nerability, and risk affecting differ- areas of concern (requiring input from ent areas (requiring experienced engineers, field technicians, community GIS analysts and specialists in development officers, census officers) numerical landslide modeling) —— Main steps: 2. Compare the results obtained with an 1. Conduct reconnaissance of listed com- ex ante list of at-risk communities, or munities, completing slope inventory generate a new list. forms to capture landslide hazard, 3. Confirm the community short list and exposure, and vulnerability factors. priorities for intervention using field- 2. Rank landslide hazard, exposure, and based reconnaissance methods as per vulnerability qualitatively using terms Example 1, based on expert judgment. such as low, medium, or high; or use a Agree on the method by which relative numerical scoring system. landslide risk will be assessed, then agree on 3. Confirm rankings using any available any further criteria for community selection. secondary sources of hazard data Such criteria should answer questions relating (knowledge of previous slides, aerial to whether a MoSSaiC-type intervention photos, maps relating to slope fea- would be appropriate, whether it would fit the tures), exposure (housing density and project scope or specific requirements from construction type), and vulnerability funders or the government, and whether it information (poverty surveys, census would be cost-effective. To make the decision- data). making process transparent, these criteria should be set before generating the prioritized 4. Prioritize communities on basis of list of communities. risk ranking or score. Once the list of eligible communities has • Example 2: GIS-based process for wide- been generated and confirmed via brief area or top-down selection reconnaissance of the sites, the task teams will need to carry out detailed mapping in —— Main data format: Digital spatial data each community to identify the specific relating to landslide preparatory and causes of landslides. These specific slope pro- triggering factors, past landslides, and cesses cannot be identified remotely from exposure/vulnerability of communities maps since they typically occur on scales of —— Main steps: 1–10 m, and are affected by human activity (construction, farming, etc.). The detailed 1. Conduct GIS analysis of landslide community-based mapping method is the risk: subject of chapter 5 and is the basis for the a. Using basic semi-quantitative GIS design of the physical landslide risk reduc- map analysis and index overlay to tion measures in chapter 6. CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 3 9 4.3.3 Roles and responsibilities in Task teams community selection Members of the landslide hazard assessment and engineering team, mapping team, commu- The community selection process encom- nity liaison team, and technical support team passes a wide range of disciplines and stake- may all be involved in landslide risk data holder interests. Use the following overviews acquisition and analysis. Typical tasks include of roles and responsibilities to ensure the pro- the following: cess is scientifically grounded, rigorous, and transparent. • Review the data acquired and handle pre- liminary error checking MoSSaiC core unit • Process data into appropriate formats The MCU has the following responsibilities: • Conduct field reconnaissance or data analy- • Agree on the process for community selec- sis to determine landslide hazard, and the tion, who will be involved in decision mak- exposure and vulnerability of communities ing, and how the process will be run • Combine the results of hazard and vulner- • Agree on the criteria or thresholds for ability assessments to determine overall inclusion of communities landslide risk • Identify a lead investigator for the task of • Present the risk comparison results in a for- landslide risk data acquisition and analy- mat that is accessible for decision-making sis purposes • Ensure that existing government proce- • Maintain and update hazard, exposure, vul- dures and protocols are followed (e.g., with nerability, and risk data for future use (if regard to access to and sharing of sensitive required as part of the project) data) • For selected communities, generate base • Review the outcomes of the data acquisi- maps for use in detailed community-based tion and landslide risk analysis process landslide hazard and drainage mapping • Agree on a prioritized list of communities (see chapter 5) for detailed mapping and MoSSaiC proj- ects. 4.4 LANDSLIDE SUSCEPTIBILITY For the purposes of community selection, AND HAZARD ASSESSMENT the MCU could be augmented to include land- METHODS slide risk assessment experts from local higher education institutions, and representatives Different approaches can be used to assess from ministries and agencies responsible for relative landslide susceptibility or hazard utilities (water, electricity) and census data. depending on the data, expertise, and These stakeholders should perform the fol- resources available (see above and sec- lowing: tion  3.4). Following is a brief overview of • Advise on the technical aspects of landslide some commonly used assessment methods; risk assessment these are presented in order of increasing data requirements, complexity, and level of • Provide data held by their institutions or quantification: ministries • Field-based reconnaissance and heuristic • Advise on the reliability of data (expert) ranking/scoring of landslide haz- • Contribute to the decision-making process ard (qualitative results at a detailed scale) 1 4 0    C H A P T E R 4 .   S E L E C T I N G CO M M U N I T I E S • GIS-based index overlay of digital maps 4.4.1 Qualitative landslide hazard using a heuristic approach to give landslide assessment: Field reconnaissance and susceptibility (qualitative results over hazard ranking methods medium to regional scales) Qualitative slope stability assessment methods • GIS-based landslide susceptibility and involve the systematic classification of slopes hazard assessment using probabilistic, sta- in relative terms such as high, medium, or low tistical, or deterministic methods (semi- landslide hazard or using a relative rating quantitative and quantitative results par- derived from a numerical scoring system. ticularly suited to large and medium These methods are usually based on a combi- scales). nation of expert judgment and empirical evi- Regardless of whether a simple qualitative dence (local knowledge or records of past or in-depth quantitative method is used, it is landslides). They can be used as a means of important to distinguish between landslide initial assessment of slope stability in the field susceptibility and landslide hazard: or in combination with remote sensing, GIS, and mapping methods. • Landslide susceptibility relates to the type Field reconnaissance and hazard ranking and spatial distribution of existing or poten- methods can be used for community selection tial landslides in an area. Susceptibility in one of two ways: assessment is based on the qualitative or quantitative assessment of the role of pre- • As the primary method in a bottom-up (list- paratory factors in determining the relative driven) approach, where communities have stability of different slopes or zones. The been listed by government agencies and/or magnitude and velocity of existing or poten- community representatives as requiring tial landslides may be taken into account, assistance, and where there are insufficient but the frequency or timing will not be digital map data for a top-down/wide-area specified. assessment of landslide susceptibility or hazard • Landslide hazard is the probability of a landslide (qualitatively or quantitatively • As the second stage in a top-down approach, assessed) of a certain type, magnitude, and as a means of verifying and prioritizing the velocity occurring at a specific location. communities identified via wide-area GIS- Quantitative hazard assessment takes into based susceptibility or hazard mapping. account the role of the triggering event (of a known probability) causing the landslide. Similar methods are used for detailed com- munity-based slope feature mapping once a A comprehensive list of all the potential community has been selected for a MoSSaiC data on environmental factors related to slope intervention. This in-depth mapping process stability is given in table 4.3. The relevance of is fully described in chapter 5. these data to landslide susceptibility and haz- These methods are usually applied in com- ard assessment is described, and their applica- bination with an assessment of the exposure bility at different scales is indicated. It is not and vulnerability of the elements at risk (see expected that all of these data are available section 4.5) in order to arrive at an overall for—or even relevant to—the community landslide risk rating (section 4.6). Field recon- selection process. naissance and hazard ranking methods are Most of the methods introduced in this sec- also used in the development of a national tion can be applied to both landslide suscepti- slope stability database (or risk register) for bility and landslide hazard assessment; the use in landslide management. main difference is whether the landslide prob- One limitation of this type of approach is ability is estimated for a specific location. the difficultly in achieving consistent evalua- CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 4 1 TAB L E 4. 3  Overview of environmental factors and their relevance to landslide susceptibility and hazard assessment DATA LAYER AND SCALE OF ANALYSIS GROUP TYPE RELEVANCE R M L D Slope gradient Most important factor in gravitational movements Slope direction Might reflect differences in soil moisture and vegetation Digital Slope length/shape Indicator for slope hydrology elevation Flow direction Used in slope hydrological modeling models Flow accumulation Used in slope hydrological modeling Internal relief Used in small-scale assessment as indicator for type of terrain Drainage density Used in small-scale assessment as indicator for type of terrain Rock types Lithological map based on engineering characteristics rather than stratigraphic classification Weathering Depth of weathering profile is an important factor for landslides Discontinuities Discontinuity sets and characteristics for rock slides Geology Structural aspects Geological structure in relation with slope angle and direction is relevant for predicting rock slides Faults Distance from active faults or width of fault zones is important factor for predictive mapping Soil types Engineering soil types, based on genetic or geotechnical classification Soil depth Soil depth based on boreholes, geophysics and outcrops, is crucial data layer in stability analysis Soils Geotechnical Grain size distribution, cohesion, friction angle, and bulk density are properties crucial parameters for slope stability analysis Hydrological Pore volume, saturated conductivity, PF curve are main parameters properties used in groundwater modeling Water table Spatially and temporal varying depth to groundwater table Soil moisture Spatially and temporal varying soil moisture content main component in stability analysis Hydrology Hydrologic Interception, evapotranspiration, through fall, overland flow, components infiltration, percolation, etc. Stream network Buffer zones around first-order streams, or buffers around eroding rivers Physiographic units Gives a first subdivision of terrain in zones, which is relevant for small- scale mapping Terrain mapping Homogeneous with respect to lithology, morphography, and Geomor- units processes phology Geomorphological Genetic classification of main landform building processes units Geomorphological Geomorphological subdivision of the terrain in smallest units, also (sub)units called slope facets Land-use map Type of land use/land cover is a main component in stability analysis Land-use changes Temporal varying land use/land cover main component in stability analysis Vegetation Vegetation type, canopy cover, rooting depths, root cohesion, characteristics weight, etc. Land use Roads Buffers around roads in sloping areas with road cuts often used as factor maps Buildings Areas with slope cuts made for building construction are sometimes used as factor maps Source: van Westen, Castellanos Abella, and Sekhar 2008. Note: R = regional; M = medium; L = large; D = detailed; ï?® = highly applicable; ï?® = moderately applicable; ï?® = less applicable. 1 42    C H A P T E R 4 .   S E L E C T I N G CO M M U N I T I E S tions of landslide hazard. Different practitio- from such an event (see section 4.5 on vul- ners will inevitably make different judgments nerability assessment). of the same slope and will rank hazards differ- 3. Record observations consistently and ently across wide areas. In several countries, clearly, using a slope reconnaissance form numerical scoring systems have been devel- designed for this purpose. Sketch or take oped to enable even relatively inexperienced photos of key slope features and, if the data engineers and geologists to carry out consis- are to be added to a digital map, use a hand- tent and repeatable slope assessments. Exam- held global positioning system (GPS) ples of numerical scoring systems are receiver to record their location. At this described at the end of this subsection. stage, detailed mapping of the community General procedure for field reconnaissance of or measurement of slope parameters is not landslide hazard necessary; this will be carried out if the community is selected for a landslide miti- 1. Obtain any existing maps of the area and gation intervention (see chapter 5). secure permission to access the site if nec- 4. Make a judgment as to the level of landslide essary. Traverse the area on foot (figure 4.2) susceptibility—high, medium, low—and the and identify any features that indicate a likelihood of the occurrence of the hazard, landslide hazard. Consider slope angle, or use a numerical scoring system to derive material type and properties (soil forma- a hazard score. Different methods for doing tion, weathering and strength, permeabil- this are described below. ity), slope hydrology and drainage (conver- gence zones, drainage routes), vegetation, Frameworks for ranking landslide hazard loading, and existing or past landslides (as Due to the inherent subjectivity of qualitative described in chapter 3). methods, it is important to make the slope 2. Identify any elements exposed to the poten- assessment process as transparent as possible tial or existing landslide hazard and deter- by recording observations and the basis for mine their vulnerability (degree of damage) judgments clearly and systematically. Basic forms simply act as a record of observations; more sophisticated methods allow different FI G U R E 4.2  Field reconnaissance slope features to be numerically scored on the basis of their likely contribution to slope sta- bility/instability. A standard slope reconnais- sance form should be developed for this pur- pose (table 4.4). It could be adapted from existing forms used in other countries. Once the slope features have been recorded in the agreed-upon format, landslide hazard should be assessed in terms of potential land- slide type, likelihood, and magnitude. The likelihood of a landslide is usually described in terms of the expected frequency or return period, or in qualitative terms with respect to other slopes. An example of a landslide likeli- hood rating system is given in table 4.5. The magnitude of the potential landslide consists of at least two components: an esti- mate of the potential size of the failed area (or volume of ground displaced; see the following CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   1 43 TA BLE 4 .4  Typical sections of a slope reconnaissance form SLOPE FEATURE DESCRIPTION Slope angle • Gently sloping (< 15°) to very steep (> 45°) Topography • Concave/convex/planar/hummocky/complex/terraced Slope-forming • Degree of weathering as indicator of strength (from bedrock to residual soils and material colluvium) • Depth of soil to bedrock Erosion • Type: indistinct/rill/gully/piping/washout • Extent: isolated or small areas/multiple features/almost continuous area Geological • Outcropping of bedrock features • Presence of joints • Joint spacing: wide (massive)/medium (blocky)/close (fractured) Ground • Extent: isolated/substantial moisture • Location: base of slope/midslope/convergence zone/strata interface/other • Occurrence: only after rainy/wet season/all year Seepage • Extent: isolated/substantial • Location: bedding planes/joints/shear zone/strata interface/other • Water: clear/muddy Vegetation • Type (%): grass/shrub/forested/cultivated/other • Density: sparse/moderate/dense Site stability • Known: past landslide activity/landslide-prone area • Indicators: tilting of trees or structures/hummocky ground/tension cracks/other Adverse human • Slope excavation/loading/removal of vegetation/irrigation/mining/water leakage/ impact drainage failure Sketch • Slope cross-section indicating geometry, strata, geological features, seepage, ground moisture, vegetation, site stability indicators, adverse human impacts, and location of any elements at risk • Slope plan indicating the above features and location of previous landslides Landslide • Landslide type: fall/topple/slide/flow/complex hazard • Slope material: bedrock/unconsolidated material (see chapter 3) • Landslide likelihood (see table 4.5) • Landslide magnitude: estimate size of potential failure and potential distance of runout (Finlay, Mostyn, and Fell 1999) • Hazard score (if using numerical scoring system) equation given by Cruden and Varnes 1996), W = Maximum width between flanks of land- and some description of what will happen to slide perpendicular to length, L the failed material such as the distance/depth/ L = Minimum distance from landslide crown speed/volume of runout. to toe Volume of ground displaced = 1/6Ï€ × D × W × L Empirical methods for estimating the travel distance and depth of failed material require Where: few measurable parameters. If the landslide D = Maximum depth to slip surface below type is properly identified and the relevant original ground surface equations used, Wong and Ho (1996, 419) 1 4 4    C H A P T E R 4 .   S E L E C T I N G CO M M U N I T I E S TAB L E 4.5  Example of a landslide likelihood rating system INDICATIVE TOTAL ANNUAL HAZARD SCORE DESCRIPTION OF LIKELIHOOD PROBABILITY LEVEL The event is expected to occur and may be triggered 5 0.5 Very high by conditions expected within a 2-year period The event is expected to occur and may be triggered 4 0.5–0.2 High by conditions expected within a 2- to 5-year period The event will probably occur under adverse conditions 3 0.2–0.02 Moderate expected over a 5- to 50-year period The event could possibly occur under adverse 2 0.02–0.002 Low conditions expected over a 50- to 500-year period The event is unlikely to occur except under very 1 0.002–0.0002 Very low adverse circumstances over a 500- to 5,000-year period Source: Indicative measures of landslide hazard based on Australian Geomechanics Society 2000 and Ko Ko, Flentje, and Chowdhury 2004. assert that such an approach provides a “quick nities in developing countries. However, three and realistic assessment of the likely rangeâ€? of case studies are presented below to exemplify runout distances and depths. An approach the general principles of this class of slope sta- such as that by Finlay, Mostyn, and Fell (1999) bility assessment. These principles are as fol- requires three parameters that can be readily lows: estimated in the field or modeled: initial slope • The aim of the field study should be clearly angle, the maximum depth to the potential slip defined, primarily so as to develop a priori- surface, and the height of the landslide crest tized list of slopes in specific communities above the base of the slope. See section 3.3.2 for a definition of these landslide features. but also potentially to lead to the establish- If a numerical scoring system has been ment of a national database of slopes, used, the values for landslide likelihood and observed landslides, and slope stabilization magnitude should be summed to give a total works. hazard score. Otherwise, the level of hazard • The data requirements and assessment should be described relative to other slopes method should be tailored to local condi- using terms such as high, moderate, or low, tions (slope types, landslide types, local and provide the rationale for their assessment. knowledge of landslides). Once community vulnerability to landslides has been assessed (section 4.5), the hazard • The assessment method should be formal- score or ranking is combined with the vulner- ized to enable the training of field techni- ability score or ranking to provide an indica- cians and the consistency of data collection tion of the overall landslide risk posed to each across field teams and over time. community. The following three case studies exemplify- Examples ing these principles are drawn from Hong Kong SAR, China; Australia; and the United The details of site-specific slope assessment States. methods and resulting slope inventories are rarely published by governments. In particu- • Example 1: Geotechnical Engineering lar, there do not appear to be examples of sys- Office, Hong Kong SAR, China. Hong Kong tematic field-based methods for qualitative SAR, China, is a world leader in terms of its assessment of slope stability in urban commu- establishment of a comprehensive slope CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 4 5 and landslide database, the assessment of Liang (2007) provides a helpful review of landslide hazard and risk, and management several of these methods, and of the slope of manmade and natural slopes. The New management framework developed in Priority Ranking System is used for assess- Hong Kong SAR, China (see above). ment of soil cut slopes, rock cut slopes, Included in the report’s appendixes are retaining walls, and fill slopes. For each landslide hazard reconnaissance forms slope type, a field team records the detailed used by the Ohio Department of Transpor- slope geometry, exposed slope materials, tation. While not directly applicable to slope protection and drainage, signs of urban landslides in developing countries, instability, engineering judgment as to the this report demonstrates the principles of hazard posed, and the location of facilities site-based assessment of slopes and the use (buildings and roads) with respect to the of this information in prioritizing expendi- slope. Technicians and engineers use com- ture on landslide risk reduction. putation sheets to assign numeric scores to each slope characteristic and derive insta- 4.4.2 Qualitative landslide susceptibility bility and consequence scores. Slopes can mapping: GIS index overlay methods then be prioritized for remediation mea- sures, maintenance, or monitoring (Cheng The stability of a slope is related to environ- 2009). mental factors such as slope angle, topogra- phy, drainage (on the surface and in the • Example 2: University of Wollongong, ground), soil type, geological characteristics, Australia. Ko Ko, Flentje, and Chowdhury land use, and vegetation cover. In many coun- (2004) report on a method for assessing the tries, there are digitized maps of these envi- stability of four classes of slopes: natural ronmental factors available at small (regional) slopes, embankments, rock slopes or rock scales of 1:250,000 to 1:100,000, medium cuttings, and soil cuttings. They include a scales of 1:50,000 to 1:25,000, and—some- sample field data sheet for recording the times—at large scales of 1:10,000. If GIS soft- characteristics of natural slopes and assign- ware and expertise are also available, it is pos- ing numeric scores to describe their influ- sible to analyze digital maps and produce ence on landslide hazard. Five categories of landslide susceptibility, hazard, or risk maps relative hazard are defined (from very high at these scales. The four main classes of GIS- to very low) which relate to the total score. based landslide assessment are heuristic A nominal landslide probability is then (expert-based), probabilistic, statistical, and identified based on the score and expert deterministic. judgment. This hazard rating can then be This subsection outlines the basic princi- combined with a consequence (vulnerabil- ples of GIS-based heuristic landslide suscepti- ity) score (also described in the paper) to bility mapping methods and presents related give an indication of the relative landslide case studies. These methods are closely related risk associated with a particular slope. The to the numerical scoring approach often used authors conclude that, by using this method, in field reconnaissance in that scores (an the careful observation and expert judg- index) are assigned to different slope, soil, ment of slope characteristics can provide a geology, drainage, and land cover characteris- rapid means for prioritizing slopes for more tics. These layers are then overlaid, and the detailed landslide assessment and risk influence of the various environmental factors reduction. weighted to reflect their importance in deter- • Example 3: U.S. Federal Highway Admin- mining slope stability. This procedure is com- istration. Several U.S. states have devel- monly called index-overlay analysis. GIS map- oped field-based slope assessment methods ping approaches enable the assessment of focusing on the risk to roads and road users. slope stability over continuous large areas, 1 4 6    C H A P T E R 4 .   S E L E C T I N G CO M M U N I T I E S rather than just considering individual sites. these are not reviewed here, as they can Because the GIS environment allows many represent a significant financial or time layers of information to be added, a landslide investment which may not be within the susceptibility/hazard map can be added to a scope of the project. vulnerability map to derive an overall risk 2. Convert the digital data layers into the cor- map. rect format for the chosen GIS platform. It With heuristic mapping approaches, may be necessary to geo-reference, trans- expert knowledge of the local environmental form, or reproject the data so that all the factors for landslides is essential. Ideally, if layers are in the same coordinate system the locations and types of previous landslides and geographical projection. Verify the are known and mapped, this information can accuracy and completeness of the data, and be used directly to derive appropriate weights make any necessary corrections. for the different environmental factors on each layer of the landslide hazard map. In 3. Use the elevation data to generate a digital many countries, a record of landslides is not elevation model in raster or vector format always kept or may be incomplete. In the (grid-based or triangular irregular net- absence of a landslide inventory, the analyst work). Use tools within the GIS environ- must apply local knowledge and expert judg- ment to derive key slope stability factors ment in assigning weights to the various envi- from the digital elevation model such as ronmental factors. This results in a qualita- slope angle, aspect, and length; internal tive map indicating relative landslide relief; and drainage routing. susceptibility. 4. Process other map layers to derive useful Limitations of GIS-based approaches are information. Geology maps can be reinter- related to the availability, quality, and scale of preted in terms of engineering geological the digital data and the expertise of the ana- classifications (relating to rock composition lyst. Keep in mind that landslide processes and strength). Soil depths and strengths can tend to be highly localized and cannot usually sometimes be inferred or approximated be captured at the wide-area scale. from maps of soil erosion and soil type. Note that a landslide susceptibility map Despite the importance of soil properties simply identifies the spatial variation of differ- for predicting slope stability, there are often ent ensembles of slope characteristics and very little direct data on soil strength, how landslide prone these slopes are in rela- hydrology, or depth over wide areas. In tion to each other. A landslide hazard map many cases, the limited data on soils will contains more information by indicating both need to be augmented by local knowledge the spatial and temporal likelihood of land- and by verifying soil characteristics at slide occurrence—that is, the location and tim- selected sites. ing of potential landslide events. 5. For each environmental factor, convert the General procedure for GIS index overlay range of values of the data in that layer into 1. Acquire any available digital data relating to an index that describes the relative contri- the environmental factors associated with bution to slope stability. Low index values slope stability, including elevation data (e.g., may be assigned where the characteristic of contour maps), geology, soil, and land-use the environmental variable is associated maps. If important data relating to a partic- with stable slopes (such as a strong soil or ular environmental factor are not available bedrock); high index values indicate an in a digital format but do exist in hard copy, association with less stable slopes (e.g., these may need to be digitized. Numerous weak soils). Index each factor (GIS layer) in field-based and remote-sensing methods this way—from flat land to steep slopes, exist for generating digital spatial data; shallow soils to deep soils, strong soils to CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N   1 47 weak soils, established deep-rooting vege- • Cuba: National Landslide Risk Assess- tation to bare land, and so on. This process ment Project. Cuba is recognized as having is similar to numerical scoring systems a more comprehensive national risk man- applied in slope reconnaissance methods. agement strategy than many other coun- Within each environmental factor or layer, tries in the Caribbean region. However, normalize the index values from 0 to 1. because losses from landslides remain high, in 2004 the National Civil Defense organi- 6. Apply a weighting to each of the normal- zation of Cuba and the Institute of Geology ized indexed layers, and overlay them by and Paleontology initiated a new national combining them to derive an overall land- landslide risk assessment project. In the slide susceptibility map. The higher the total score, the more susceptible the terrain absence of a sufficient national landslide unit or grid cell is to landslides. Use experi- inventory, a qualitative approach was taken: ence and local knowledge to determine the application of spatial multicriteria eval- how important each class of environmental uation techniques, in a GIS environment, to factor is in influencing slope stability and to develop a national landslide risk index map. assign different weights to the layers Castellanos Abella and van Westen (2007) accordingly. Various methods have been report the development and implementa- developed for systematically assigning tion of this approach, which is briefly sum- weights; these include the following: marized below. • Direct methods, based on expert opin- Five landslide susceptibility and five vul- ion and field experience nerability indicators were digitally mapped at a cell size of 90 × 90 m. Each indicator • Pair-wise, using a comparison matrix in was standardized and weighted by experts which each environmental factor is according to its contribution to landslide taken in turn and compared with each susceptibility or vulnerability in order to other factor to assess the most signifi- produce a measure of landslide risk. Three cant contributor to slope stability within weighting methods were used (direct each pair weighting, pair-wise comparison, and rank • Ranking, ordering environmental fac- ordering), and the weights combined to tors according to their expected influ- produce a landslide risk index. The result- ence on slope stability and then normal- ing map is used by local authorities to target izing the ranked list between 0 and 1 high-risk zones that require further detailed landslide investigation so as to identify • Indirect methods, using statistical appropriate landslide risk management methods to give weights based on data strategies (figure 4.3). for previous landslides and the inferred causal factors. • Cuba: Medium-scale qualitative assess- The resulting index overlay map presents ment of landslide susceptibility. A second the relative landslide susceptibility of different helpful example from Cuba is the qualita- terrain units (in the case of vector maps), or tive assessment of landslide susceptibility grid cells (raster maps) at a resolution deter- in San Antonio del Sur, Guantánamo, at a mined by that for the original digital data and scale of 1:50,000. The first stage of the anal- any GIS transformation of that data. ysis was the preparation of a geomorpho- logical map from aerial photos and field- Examples work. The project identified 603 terrain The following examples, both from Cuba, mapping units of homogenous geomorpho- illustrate GIS-based landslide susceptibility logical origin, physiography, lithology, mor- assessment. phometry, and soil type. The resulting 1 4 8    C H A P T E R 4 .   S E L E C T I N G CO M M U N I T I E S FI G U R E 4. 3  Method for developing a national landslide risk index map for Cuba Goal Subgoals Indicators susceptibility hazard conditions slope angle index geology land use triggering factors earthquakes risk index rainfall vulnerability social population index economic production risk evaluation environmental protected areas housing national landslide physical transportation mitigation plan Source: Castellanos Abella and van Westen 2007. insight into local factors contributing to Probabilistic approaches landslides allowed for the development of Probabilistic approaches require a compre- weights for mapping landslide susceptibil- hensive inventory of past landslides—their ity. Again, three weighting methods were location with respect to environmental factors explored—direct weighting, pair-wise com- (topography, geology, soils, drainage, etc.) and parison, and rank ordering. This heuristic their timing with respect to triggering factors identification of local terrain mapping units (such as rainfall events). In many cases, they and related observations on slope also include information on the damage stability,enabled the generation of a qualita- caused, thus allowing the vulnerability of ele- tive landslide susceptibility map at a more ments at risk to be inferred. Some of the best detailed resolution than would have been examples of national landslide databases can possible with the conventional index-over- be found in Canada; Colombia; France; Hong lay method applied at the national scale Kong SAR, China; Italy; and Switzerland. (Castellanos Abella and van Westen 2008). Analysis of these data within a GIS setting 4.4.3 Semi-quantitative and quantitative (and often in combination with heuristic landslide susceptibility and hazard methods) can allow the prediction and map- mapping methods ping of future landslides in terms of mean recurrence interval, landslide density, and The third group of GIS-based landslide hazard exceedence probability. mapping methods are more data intensive and Statistical methods require higher levels of scientific expertise than the qualitative approaches described Statistical methods also require data on past above. Probabilistic, statistical, and determin- landslides—in this case, the role of individual istic modeling methods can provide semi- environmental factors, or combinations of quantitative or quantitative measures of land- factors, in contributing to slope failures is sta- slide hazard that include indicative or tistically evaluated. Thus, landslide suscepti- numerical predictions of landslide probability. bility can be indirectly inferred by applying These methods are briefly introduced here; these causal relationships over wide areas. teams with the requisite level of expertise are Bivariate statistical approaches, such as presumably already familiar with these meth- weights of evidence methods, consider each ods and their data requirements. causal map in turn in order to derive weight- CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 4 9 ing values for that environmental factor. deterministic modeling of slope stability. These methods are widely employed in con- These methods are most appropriately applied junction with heuristic methods. Multivari- over small areas, such as river catchments or ate approaches use methods such as logistic subcatchments; and at detailed scales, since regression, artificial neural networks, and they require large amounts of good quality fuzzy logic to determine the relative contri- spatially distributed data relating to topogra- bution of all the causative environmental fac- phy, soil depth and strength, and hydrological tors in determining the landslide hazard for a properties. A digital elevation model is used to defined land unit. determine rainfall and surface water infiltra- Limitations of statistical methods include tion, groundwater levels, and pore water pres- the inherent generalization of landslide caus- sures. A typical distributed deterministic ative factors—the assumption that the same model uses a simple infinite slope stability combination of factors will cause landslides equation in conjunction with the two-dimen- throughout the study area. This limitation is sional hillslope hydrology calculations to magnified if the data on past landslides do not determine the factor of safety for each map- differentiate between landslide types, if the ping unit or grid cell. landslide data are incomplete, or if the envi- Examples of deterministic models include ronmental factor maps are not sufficiently the shallow landsliding model (SHALSTAB) detailed to capture localized variations. developed by Montgomery and Dietrich (1994) and available as an ArcScript for use in Deterministic approaches ArcView GIS; and the Stability Index Mapping Deterministic approaches address landslide (SINMAP) model developed by Pack, Tarbo- hazard in terms of underlying physical pro- ton, and Goodwin (1998), which is also avail- cesses. For engineering and geotechnical able as an ArcView GIS extension. applications, deterministic modeling is usually Figure 4.4 shows the results of such an anal- undertaken at the scale of individual slope ysis for the assessment of debris flow hazard in cross-sections. However, in a GIS environ- Tegucigalpa, Honduras. The spatial data for ment, the ability to represent slope parameters this study by Harp et al. (2009) included a dig- over a wide area allows spatially distributed ital elevation model (for deriving slope angle), F IG U R E 4 .4  Quantitative GIS-based hazard map for Tegucigalpa, Honduras Source: Harp et al. 2009. 1 5 0    C H A P T E R 4 .   S E L E C T I N G CO M M U N I T I E S a geological map (for deriving material The vulnerability of exposed elements is strength), and an inventory of debris flows expressed in terms of the potential degree of triggered by Hurricane Mitch in 1998. An infi- damage (or loss) with respect to the magni- nite slope stability model (based on the limit tude (or intensity) of a given landslide. equilibrium approach described in chapter 3) MoSSaiC projects are intended for the most- was used to predict the slope factor of safety physically and -socioeconomically vulnerable and hence determine the debris flow hazard communities. As with landslide hazard assess- for different hillslopes. ment, the scale of this assessment can vary Deterministic methods can also be applied from regional to detailed household level, and in the prediction of landslide runout—travel the data requirements, methodology, and out- distance, velocity, and depth of landslide puts will vary accordingly. Exposure is often debris. The development and application of considered in conjunction with, or as an inte- such approaches require extensive data and gral part of, vulnerability (Crozier and Glade significant expertise, and are therefore not 2005). necessarily appropriate for use in community Table 4.6 identifies the ways in which the selection. exposure and vulnerability of different ele- ments at risk may be represented at different spatial scales. Of particular relevance to 4.5 ASSESSING COMMUNITY MoSSaiC are data on buildings, population, VULNERABILITY TO and economic factors that describe the physi- LANDSLIDES cal and socioeconomic exposure and vulnera- bility of urban communities to landslides. Having identified the landslide susceptibility At medium mapping scales, the physical or hazard for a list of communities, or on a exposure and vulnerability of the community wider spatial scale using GIS-based methods, can be described simply in terms of how the next stage is to consider what the conse- many buildings (houses) might be affected by quences of a landslide event would be in terms a landslide event. At a more detailed scale, for of the exposure and vulnerability of different a given landslide location and magnitude, the elements (people and property) to that hazard. physical exposure and vulnerability of a The overall landslide risk is the combination house may be described in terms of how eas- of hazard, exposure, and vulnerability. ily it could be damaged. For example, if hit by Exposure describes the location of a par- a small landslide, a concrete house with good ticular element with respect to the potential foundations may be less likely to collapse landslide—whether it is on the upper or side than a wooden structure with poor founda- margins of the slide, within the failed mass, or tions. The physical vulnerability of people in the path of the debris. In selecting commu- within a community relates to the level of nities for potential MoSSaiC interventions, injury or loss of life; this is a very difficult both the number of houses exposed to each aspect of vulnerability to assess since it particular landslide hazard and the density of requires the combined spatial and temporal housing within that hazard zone (often prediction of both the landslide event and the expressed as the proportion of land coverage exposure of people to that event. by houses) must be noted. Housing density is The socioeconomic vulnerability of a com- particularly significant, because MoSSaiC munity to landslides is related to the ability of projects involve the construction of a network households to recover from a landslide. This of surface water drains to improve slope stabil- recovery might involve rebuilding part or all of ity and reduce the hazard to multiple house- a house, replacing possessions, finding a dif- holds. The greater the housing density, the ferent means of income (if tools or stock have more households will benefit from the drain- been lost), or moving to a different location. age intervention. While not synonymous with poverty, socio- CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 5 1 TAB L E 4.6  Main elements at risk used in landslide risk assessment studies and their spatial representation at four mapping scales SCALE OF ANALYSIS ELEMENT Small Medium Large Detailed Buildings By municipality Mapping units Building footprint Building footprints • Number of buildings • Predominant land use • Generalized use • Detailed use • Number of buildings • Height • Height • Building types • Building types • Construction types • Quality/age • Foundation Transportation General location of Road and railway All transportation All transportation networks transportation networks networks, with general networks with detailed networks with detailed traffic density informa- classification, including engineering work and tion viaducts, etc., and traffic detailed dynamic traffic data data Lifelines Main power lines Only main networks Detailed networks Detailed networks and • Water supply • Water supply related facilities • Electricity • Wastewater • Water supply • Electricity • Wastewater • Communication • Electricity • Gas • Communication • Gas Essential By municipality As points Individual building Individual building facilities • Number of essential • General characterization footprints footprints facilities • Building as groups • Normal characterization • Detailed characterization • Buildings as groups • Each building separately Population By municipality By ward By mapping unit People per building data • Population density • Population density • Population density • Daytime/nighttime • Gender • Gender • Daytime/nighttime • Gender • Age • Age • Gender • Age • Age • Education Agriculture By municipality By homogeneous unit By cadastral parcel By cadastral parcel, for a data • Crop types • Crop types • Crop types given period • Yield information • Yield information • Crop rotation • Crop type • Yield information • Crop rotation and time • Agricultural buildings • Yield information Economic By region By municipality By mapping unit By building data • Economic production • Economic production • Employment rate • Employment • Import/export • Import/export • Socioeconomic level • Income • Type of economic • Type of economic • Main income types plus • Type of business plus activities activities larger-scale data larger-scale data Ecological Natural protected areas Natural protected area General flora and fauna Detailed flora and fauna data with international approval with national relevance data per cadastral parcel data per cadastral parcel Source: van Westen, Castellanos Abella, and Sekhar 2008. economic vulnerability is often related to the likely to live in landslide-prone areas than level of poverty: poorer households will find it wealthier households, and in houses that are more difficult to recover. In many ways too, less resilient to the physical impact of a land- socioeconomic vulnerability is closely related slide. Poverty assessments can sometimes pro- to the exposure and physical vulnerability of a vide an indication of a community’s vulnera- community since poorer households are more bility. 1 52    C H A P T E R 4 .   S E L E C T I N G CO M M U N I T I E S The following subsections outline two • The number of houses and people likely to broad approaches to assessing the potential be exposed to the landslide and debris consequences of landslides with a view to • The housing density (this helps with the determining which communities have the assessment of the possible cost-effective- greatest exposure and vulnerability. ness of constructing a drainage network) • Field reconnaissance and heuristic (expert- • The potential physical damage to individ- based) ranking/scoring of community and ual houses based on their construction type household exposure and vulnerability to (if there is sufficient knowledge of past landslides landslide impacts and the resilience of • GIS-based methods using land-use maps to structures to such impacts; figure 4.5) determine community exposure, and cen- • The cost of the potential landslide damage sus data to assess vulnerability (qualitative (if the approximate value of the elements at to semi-qualitative results over medium to risk is known). regional scales). Use these guidelines to identify a method- F IGUR E 4 . 5  Resilience of structures ology compatible with available data and depending on construction type expertise, and that can be interfaced with landslide hazard information in terms of its format (list or map) and spatial scale. 4.5.1 Field reconnaissance and vulnerability ranking methods Field reconnaissance and ranking methods were introduced in section 4.4.1 as a means for rapid assessment of landslide hazard by a team of experts. Similar methods can be applied to a. Minor landslide where the impact of the assess community exposure and vulnerabil- debris has damaged a concrete home. ity—either qualitatively (e.g., as high, moder- ate, or low), or quantitatively (using a numeri- cal scoring system). Hazard, exposure, and vulnerability measures can be combined to rank overall landslide risk. General procedure for field reconnaissance of vulnerability Specific procedures relating to the assessment of community exposure and vulnerability to landslide hazards are highlighted here; see section 4.4.1 for the general procedure for field reconnaissance. If a landslide hazard has been identified, the team should have already estimated the spatial extent of the landslide-prone area and the potential downslope extent of the failed material. On the basis of this assessment, esti- b. Minor landslide where the impact of the mate the physical exposure and vulnerability debris has destroyed a wooden home. in terms of the following: CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 5 3 Consider the overall socioeconomic vulner- slope assessment process as transparent as ability of the community using locally relevant possible by recording observations and the indicators such as basis for judgments clearly and systemati- cally. Basic forms can be used to record • the size of houses and plots, house con- observations; more sophisticated tools allow struction type, and ownership of vehicles; different community and household charac- • the presence or absence of basic infrastruc- teristics to be numerically scored on the ture such as publicly supplied piped water, basis of their likely contribution to exposure provisions for sanitation and waste disposal, and vulnerability. The task team should electricity, and paved roads and paths; and develop a standard community reconnais- sance form for this purpose. The typical sec- • evidence of unemployment, low levels of tions of a slope reconnaissance form that educational attainment, overcrowded hous- relate to vulnerability assessment are out- ing, and isolated or marginalized groups lined in table 4.7. (such as the elderly or disabled). Based on these observations, rank physical Semi-quantitative measures of socio- vulnerability to the potential landslide hazard, economic vulnerability (based on census data estimating how much physical damage could or community questionnaires) are outlined in be caused. This can be done either qualita- section 4.5.2; at this stage, on-site application tively (high, moderate, or low), or quantita- of such methods at the household level would tively (from 0 to 1—no loss to total loss), using be time consuming, and may be more appro- a scoring system such as that illustrated in priate once the selection of individual commu- table 4.8. nities has been confirmed. Similarly, for areas of the community potentially exposed to landslide hazard, Frameworks for ranking vulnerability to develop a qualitative or quantitative scoring landslides system to indicate the socioeconomic vulner- Given the inherent subjectivity of qualita- ability. tive methods, it is important to make the TA BLE 4 .7  Typical sections of a slope reconnaissance form that relate to vulnerability assessment VULNERABILITY COMPONENT DESCRIPTION • Number of houses on landslide-prone area Exposure of elements to • Number of houses in potential landslide runout zone landslide hazard • Density of houses exposed to the landslide hazard • Number of houses likely to be lost Physical vulnerability of • Number of houses likely to be significantly damaged elements to landslide hazard • Number of houses likely to need minor repairs • Number of households likely to need relocating Various possible measures including: • Financial resources/level of poverty (quality of housing, ownership of possessions) • Presence/absence of basic infrastructure Socioeconomic vulnerability • Level of unemployment (adults not at work) • Level of education (children not at school) • Level of overcrowded housing • Existence of marginalized groups 1 5 4    C H A P T E R 4 .   S E L E C T I N G CO M M U N I T I E S Data sources TAB L E 4.8  Example of a numerical scoring system for landslide damage to houses At regional and medium scales, the number of buildings per area may be derived from census SCALE OF DISTANCE (m) information or from land-use maps (identify- LANDSLIDE (m3) < 10 10–50 > 50 ing urban or semi-urban residential areas); < 10 2 0.3 0.2 0.1 and at larger scales, individual building foot- 10 –10 2 3 0.4 0.3 0.2 prints may be indicated. Since the most vul- 103–104 0.6 0.5 0.4 nerable communities are often unauthorized > 10 4 1.0 0.9 0.8 or informal settlements, it is likely that maps of Source: Dai, Lee, and Ngai 2002. buildings will be out of date. In such cases, aerial photos may be used supplement this Note: Damage is indicated on a scale of 0 (no loss) to 1 (total loss) depending on landslide scale and information. At the scales required for the proximity. community selection process, the physical vulnerability of communities may simply be 4.5.2 GIS-based mapping methods for derived as the likely number of buildings to be vulnerability assessment affected by a landslide (and assuming equal damage). GIS software is designed for the overlay of dig- For the purpose of community selection it ital spatial data, the analysis of that data, and may be helpful to use poverty as an indicator the generation of combined maps. Thus, if the for comparing the relative socioeconomic vul- location of communities is available as a digital nerability of communities (although it is rec- map, this information can be used in conjunc- ognized that poverty and vulnerability are not tion with landslide susceptibility or hazard synonymous). In many countries, poverty or maps to determine exposure to landslides. The welfare indicators have been derived that use number or density of buildings within these information from surveys or the national cen- landslide zones can be used as a proxy for the sus. Poverty surveys and census data are often physical vulnerability of communities and the geo-referenced to allow mapping of different likely cost-effectiveness of a drainage inter- levels of aggregation such as at the level of vention; the socioeconomic vulnerability (or municipal and enumeration districts. It is resilience) of communities can be represented sometimes possible to map this information at by some form of poverty measure. the community and street-level scales—the Vulnerability may be expressed in qualita- scale of the potential landslide hazard and mit- tive terms (such as high, medium, or low), igation measures. semi-quantitative terms (e.g., using a poverty index), or quantitative terms (such as the Frameworks for assessing poverty number of houses likely to be damaged and the estimated value of the damage). Quantitative The most straightforward poverty measures measures are often used to indicate direct simply consider household income and con- damage, but it is less easy to quantify indirect sumption expenditure as indicators of the damage, such as the social, emotional, long- level of welfare. More sophisticated measures term economic damage to individuals and the incorporate other indicators. For example, wider community. Thus, semi-quantitative Human Development Index (HDI) of the poverty indicators are often used as a proxy for United Nations Development Programme is a vulnerability to direct and indirect damage. composite of income, education, and health It is helpful if the spatial scale and level of measures designed to facilitate comparison of quantification of the vulnerability assessment deprivation and development levels nationally is matched to the scale and output format of and globally. Locally derived poverty indica- the hazard mapping exercise to enable calcu- tors may also be available that have been tai- lation of the overall landslide risk. lored to the specific characteristics of a par- CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 5 5 ticular region or country. Table 4.9 illustrates and present either as a list or import into GIS the typical components of a locally derived to create a map. poverty index. These measures can be applied both in the field (using a household questionnaire), or 4.6 ASSESSING LANDSLIDE RISK using GIS (by acquiring geo-referenced cen- AND CONFIRMING sus data at the least aggregated, most detailed, COMMUNITY SELECTION level possible). The required census variables may initially be processed in the census data- Landslide risk is a product of the level of land- base software using available search and slide susceptibility or hazard and the vulnera- query protocols. For more complex analysis, bility of the elements exposed to damage by export the data to a spreadsheet. Finally, sort that hazard (the potential landslide conse- the list of communities according to socio- quences). The previous two sections have out- economic vulnerability (poverty in this case) lined a range of methods for deriving landslide TA BLE 4 .9  Typical components of a locally derived poverty index MAXIMUM ITEM CLASSIFICATION SCORE SCORE FOR ITEM Wall type Brick/block/concrete 3 Wood and concrete 2 3 Wood 1 Wattle/tapia/makeshift 0 Toilet type WC to sewer/cess pit 1 1 Pit latrine/none 0 Light source Electricity/gas 1 1 Kerosene/none 0 Possessions TV, telephone, video, stove, refrigerator, washing 0.5 each machine 4 Car/pick-up 1 No. persons <1 3 per 1–1.99 2 bedroom 3 2–3 1 3.01 or more 0 Education Tertiary/university 5 of head of Secondary complete 4 household Secondary incomplete 3 5 Primary complete 2 Primary incomplete 1 None 0 No. of 1 3 employed to 0.49–1 2 total no. of 3 persons 0.25–0.5 1 < 0.25 0 Maximum total score: 20 Source: Government of St. Lucia 2004. 1 5 6    C H A P T E R 4 .   S E L E C T I N G CO M M U N I T I E S susceptibility or hazard, exposure and vulner- ability in qualitative, semi-quantitative, and TAB LE 4 .10  Example of a risk rating matrix quantitative terms; in list or map-based for- OVERALL PHYSICAL AND SOCIOECONOMIC mats; and using field reconnaissance or GIS HAZARD VULNERABILITY RATING processing of digital spatial data. This section RATING Very high High Medium Low Very low brings these outputs together to derive an Very high 5 5 4 3 2 assessment of landslide risk to enable selec- High 5 4 4 3 2 tion of the most appropriate communities in Medium 4 4 3 2 1 which to initiate MoSSaiC projects. Low 3 3 2 1 1 Very low 2 2 1 1 1 4.6.1 Combining the hazard and vulnerability information Depending on the approach taken for assess- ing landslide hazard, expose and vulnerability, A team of landslide experts/engineers or use one of the following methods to combine geotechnicians and a social scientist or com- these assessments and derive the overall land- munity development practitioner should visit slide risk to communities. each of the short-listed communities and use rapid field reconnaissance to confirm the Field reconnaissance methods selection. Complete the reconnaissance forms and assess the overall landslide risk when on site in each 4.6.2 Confirming selected communities community—assigning both hazard and vul- The task team should present the results of the nerability ratings in qualitative terms or risk comparison and analysis to the MCU according to a numerical scoring system. Com- along with the following information to sup- bine these ratings or scores to give the land- port the decision-making process: slide risk rating using a matrix such as that in • Executive summary table 4.10. Once all the communities on the list have —— A list or table of the communities in rank been visited and assessed in this way, review order of landslide risk together with the the completed reconnaissance forms and rank hazard, exposure, and vulnerability rat- the communities in order of landslide risk. ings or scores (derived from field recon- naissance results or GIS maps) GIS-based methods —— Maps of the landslide hazard, exposure, An alternative to a risk rating matrix is to vulnerability, and risk assessments if GIS overlay GIS-generated hazard and vulnera- methods have been applied bility maps to produce a composite landslide risk map. Different weights may be assigned • Appendixes to the hazard and vulnerability maps accord- —— Supporting materials detailing the data ing to the agreed-upon community selection acquisition and analysis process and pro- criteria. viding the rationale behind qualitative To identify a community short list, review heuristic (expert-based) judgments the attributes of the risk map and sort the com- munities by overall risk. Compare the risk —— Key reconnaissance data sheets or sub- assessment with local knowledge, known sidiary maps developed as part of the landslides, and past events and ask whether risk assessment process the results are realistic and reasonable or whether the method needs refining. Abstract a The MCU should review the list and decide short list of high-risk communities from the how well each of the priority communities GIS for final verification. meets the selection criteria and whether they CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 5 7 are within the scope of the project. Some of the vention against the criteria decided in sec- more technical aspects of this review may tion 4.3.2 (table 4.11). require further discussion with experts on the Finally, the MCU should report, agree, and task team. Other information (or pressures) sign off on the community short list with the from communities and their political repre- government and the project funding agency. sentatives may need to be tested against the results of the risk analysis to justify the final MILESTONE 4: list of prioritized communities. Process for community selection For each of the communities on the priority list, the MCU should provide a short summary agreed upon and communities justifying its suitability for a MoSSaiC inter- selected TAB L E 4.11  Sample justification for community selection JUSTIFICATION FOR DECISION SUITABLE FOR COST- COMMUNITY MoSSaiC EFFECTIVE NOTES Selected for MoSSaiC • A vulnerable community with multiple households exposed to landslide hazards (rotational or translational slides in weathered materials) A Yes Yes • A community-based drainage intervention is potentially appropriate for reducing the hazard • Housing density is high giving a low drain length, and construction cost, per house Selected for MoSSaiC • A vulnerable community exposed to landslide hazards (rotational or translational slides in weathered materials) as a result of surface water runoff Yes, if from roads above the community and from households combined with B Yes • A suitable location for a road drainage intervention that would protect road drainage intervention adjacent houses and the road, combined with a community-wide drainage intervention • Per house cost could potentially be high, but this would be offset by preventing loss of road (a high-cost event) Not selected for MoSSaiC • A moderately wealthy community exposed to multiple small landslide hazards (rotational or translational slides in weathered materials) in cut slopes behind houses C Yes No • Low housing density, so a community-wide drainage intervention would have a high cost per house • A more cost-effective solution would be education and enforcement of regulations relating to cut slopes, drainage, and retaining structures at the household level Not selected for MoSSaiC • Landslide hazard is caused by, and/or only affects, one house (low exposure) • The landslide hazard relates to physical processes not targeted by MoSSaiC D No No approach • An appropriate risk reduction approach would be relocation of the household, or a localized engineering intervention such as a retaining wall; not a community-based or community-wide MoSSaiC drainage intervention 1 5 8    C H A P T E R 4 .   S E L E C T I N G CO M M U N I T I E S 4.7 PREPARING A BASE MAP FOR Topographic, or contour, maps provide a DETAILED COMMUNITY useful starting point for preparing the base MAPPING map, since the scale and coordinate system are known and topographic units can be recog- nized. Many topographic maps also include Once the list of prioritized communities has land-use information and the locations of been confirmed, the mapping task team should houses, roads, paths, and drainage lines—thus compile all the spatial data available to pro- providing a head start in the detailed mapping duce a composite base map for each commu- of a community (figure 4.6b). A base map that nity. These maps will be used to identify the includes these features as vectors (points, precise localized slope processes and trigger- lines, and polygons) is usually quite clear and ing mechanisms that contribute to the land- easy to interpret; such a document is also very slide hazard in each community. This detailed easy to annotate. community mapping is undertaken in the next stage of the project (chapter 5). 4.7.2 Supporting data The base map is used both as a guide in Maps of geology, lithology, and soils can pro- locating and understanding these slope pro- vide useful supplementary data in support of cesses, and as a template to which detailed field observations and slope stability calcula- observations can be added by the community tions. In general, however, they should not be mapping team and the residents. The anno- included in the base map owing to the sheer tated base map is thus a working document in volume of information they would add. Aerial the identification of landslide causes and and satellite photos can similarly supplement potential solutions. It may be used as an input the base map, providing information on the for physically based analysis of slope stability location of houses, paths, and—sometimes— and to communicate slope stability concepts drainage routes; but the density of their infor- and project aims to the community. And, after mation and the solid coloration of these raster many revisions, it will provide the template for images can make annotation difficult (fig- the detailed drainage design and work pack- ure 4.6c). On the other hand, aerial photos are ages for construction. a very useful tool for engaging residents in dis- cussing landslide and drainage issues. 4.7.1 Useful features If field reconnaissance forms have been It is useful to work from a geo-referenced map used in the rapid assessment of landslide haz- of the community. Such a map will make it ard and vulnerability (as described in this easier to analyze the cause/effect relationships chapter), this information should be added to between slope features, processes, and land- the base map or included in the supplemen- slide triggering mechanisms, and will allow tary material. measurements to be made, other maps to be overlaid, and GPS locations to be identified. 4.7.3 Sources of spatial data Base maps should be at the most detailed If field reconnaissance was the main method- resolution possible to permit identification (or, ology for community selection and there are later, addition) of individual features such as no digital maps, photocopy and scale up any houses, paths, and drainage patterns (fig- available hard-copy maps of each community ure 4.6a). The area covered by each base map as necessary. should encompass the topographic unit within Where GIS-based mapping was used in which the community resides (i.e., the hillside the community selection, print out a high- or drainage subcatchment), since this is the resolution base map of each community. Ide- greatest area over which potential landslide ally, the base map should comprise GIS layers mechanisms and associated environmental with vector data (points, lines, and polygons) factors may operate. showing contours, roads, paths, drains, and CO M M U N I T Y- B A S E D L A N D S L I D E R I S K R E D U C T I O N    1 5 9 F IG U R E 4 . 6  Generating the base map from a topography map and an aerial photo a. A community base map prepared from the original topographic map (b) and updated using an aerial photo (c). b. A topographic map may be available. In this c. An aerial photograph of the community can be example, the main roads and some of the houses used in updating existing digital maps to create in the community are also shown. the base map and as a supplementary resource for the community mapping process. Source: Reproduced with permission of the Chief Surveyor, Ministry of Physical Planning, St. Lucia. houses. Try not to include raster layers, such Depending on the quality of the survey con- as aerial photographs or digital elevation ducted and whether the plans are geo-refer- models, or layers with soils, geology, and enced, such information can be a useful part of lithology; these data can be provided as sup- the base map. However, maps and information plementary maps. consolidated from government or other A final source of information for the base sources may not be up to date. Before these can map may be surveys and plans generated for be added, significant on-site verification and previous community projects, such as the con- further relevant detail may be needed; this struction of paths and other infrastructure. process is outlined in section 5.4. 1 6 0    C H A P T E R 4 .   S E L E C T I N G CO M M U N I T I E S 4.8 RESOURCES 4.8.1 Who does what CHAPTER TEAM RESPONSIBILITY ACTIONS AND HELPFUL HINTS SECTION Agree to the community • Become familiar with potential community selection 4.3.2; 4.6 selection process criteria approaches Funders and Coordinate with the MCU and policy makers government task team Agree to the list of prioritized • Review the report from the community selection team communities Build the community selection • Identify task team members from relevant government 4.2; 4.3 team ministries and other agencies Coordinate with the government • Review available software and existing data on landslide 4.3 task team susceptibility or hazard and community vulnerability Agree on and communicate the • Identify an appropriate assessment method process for community selection • Modify the project step template (section 2.6) MCU • Review the task team report 4.6 Finalize the prioritized list of • Finalize community selection against agreed-on selection communities criteria and report to government and funders and policy makers Coordinate with funders and policy makers • Review available software and existing data on landslide 4.4; 4.5 Agree on and communicate the susceptibility or hazard and community vulnerability process for community selection • Identify an appropriate assessment method • Modify the project step template (section 2.6) Assess landslide susceptibility or • Data acquisition and application of selected methodology 4.4 hazard Assess community exposure and • Data acquisition and application of selected methodology 4.5 Government task vulnerability teams • Combine hazard and vulnerability data to indicate 4.6 Generate a prioritized list of relative risk at-risk communities • Confirm list with site visit and rapid reconnaissance • Write report for the MCU Report to the MCU Prepare the community base • Acquire all relevant spatial data to assist in the mapping 4.7 map