TNA Guidebook Series Technologies for Climate Change Adaptation – Coastal Erosion and Flooding – Technologies for Climate Change Adaptation – Coastal Erosion and Flooding – Editor Xianli Zhu, UNEP Risø Centre Authors Matthew M. Linham School of Civil Engineering and the Environment, University of Southampton Robert J. Nicholls School of Civil Engineering and the Environment and Tyndall Centre for Climate Change Research, University of Southampton November 2010 UNEP Risø Centre on Energy, Climate and Sustainable Development Risø DTU National Laboratory for Sustainable Energy P.O. Box 49, 4000, Roskilde Denmark Phone +45 4677 5129 Fax +45 4632 1999 http://www.uneprisoe.org/ http://tech-action.org/ ISBN: 978-87-550-3855-4 Pre-production and printing: Magnum Custom Publishing New Delhi, India Photo acknowledgement: Front cover photo—Looking east as southern edge of Bay Parkway bikeway crumbles into Sheepshead Bay in Brooklyn, New York on a sunny midday. Courtesy of Jim Henderson. Accessed from Wikimedia Commons Back cover photo—Coastal erosion in Papaula Point, Maui County, Hawaii. Courtesy of Forest and Kim Starr This guidebook can be downloaded from http://tech-action.org/ Disclaimer: This Guidebook is intended to be a starting point for developing country governments, coastal zone development planners, and stakeholders who are doing technology needs assessment and technology action plans for adaptation to costal erosion and flooding due to climate change. The findings, suggestions, and conclusions presented in this publication are entirely those of the authors and should not be attributed in any manner to the Global Environment Facility (GEF), the United Nations Environment Program (UNEP), and the UNEP Risø Centre. Contents 1 Introduction and Outline of the Guidebook 1 2 Background 3 2.1 Climate Change in Coastal Areas 3 2.2 Physical Impacts of Climate Change on the Coastal Zone 3 2.3 Socio-economic Impacts of SLR 11 2.4 Summary 11 3 Adaptation Approaches, Options and Practices 12 3.1 Prioritisation of Risks and Opportunities 15 3.2 Implementing Risk Reduction 16 3.3 Reviewing the Effectiveness of Outcomes 17 4 Adaptation Technologies and Practices 19 4.1 Protection Approaches 20 4.1.1 Beach Nourishment 22 4.1.2 Artificial Sand Dunes and Dune Rehabilitation 31 4.1.3 Seawalls 37 4.1.4 Sea Dikes 47 4.1.5 Storm Surge Barriers and Closure Dams 54 4.1.6 Land Claim 62 4.2 Accommodation Approaches 69 4.2.1 Flood-Proofing 69 4.2.2 Wetland Restoration 76 4.2.3 Floating Agricultural Systems 82 4.2.4 Flood Hazard Mapping 87 4.2.5 Flood Warnings 92 4.3 Retreat Approaches 101 4.3.1 Managed Realignment 102 4.3.2 Coastal Setbacks 109 4.4 Knowledge and Capacity Building Requirements 116 4.4.1 Knowledge Requirements for Protect Approaches 117 4.4.2 Knowledge Requirements for Accommodate Approaches 120 4.4.3 Knowledge Requirements for Retreat Approaches 122 4.4.4 Sources of Knowledge 123 iii 4.5 Monitoring Technologies 125 4.5.1 Monitoring Requirements 125 4.5.2 Required Technologies 130 5 Prioritisation of Technologies and Practices 132 6 Conclusions 135 7 References 137 Appendix I: Glossary 146 Appendix II: Recommended Sources for Additional Information 149 iv List of Figures and Tables List of Figures Figure 2.1: Simplified model of landward coastal retreat under SLR (based on the Bruun Rule) 4 Figure 2.2: The process of coastal squeeze 5 Figure 2.3: SLR raises extreme water levels and increases the probability of flooding without adaptation 6 Figure 2.4: Shoreline recession caused by SLR 8 Figure 3.1: Schematic illustrations of the protect accommodate and (planned) retreat responses to SLR 13 Figure 3.2: Linkages between different typologies of coastal adaptation approach and the adaptation technologies considered in this guide 14 Figure 3.3: Conceptual framework for implementing coastal adaptation measures 15 Figure 4.1: Data illustrating beach volume at Bournemouth Beach, UK 23 Figure 4.2: Rainbow method for transferring nourishment material ashore 24 Figure 4.3: Schematic illustration of longshore drift 25 Figure 4.4: Bournemouth Beach, Poole Bay, UK 29 Figure 4.5: Coastal sand dunes at Aberffraw, Anglesey, UK 32 Figure 4.6: Simplified illustration of dune erosion caused by storm surge 33 Figure 4.7: Variation in design type of seawalls 38 Figure 4.8: Schematic cross-section illustrating seawall scour 40 Figure 4.9: A seawall as viewed from above, showing typical end effects associated with the structure 41 Figure 4.10: Bar Beach seawall, Victoria Island, Lagos, Nigeria 46 Figure 4.11: Typical sea dike cross section 47 Figure 4.12: Toe scour on sloping structures 48 Figure 4.13: Land area requirements for sea dikes 49 Figure 4.14: Schematic illustration of the double dike system utilised in Nam Dinh Province, Vietnam 53 Figure 4.15: Representative cross-section of sea dikes in Nam Dinh Province, Vietnam 54 Figure 4.16: Closure dam under construction at Jamuna river, Bangladesh 55 Figure 4.17: Schematic illustration of how storm surge barriers and closure dams prevent coastal flooding 56 Figure 4.18: The main methods of land claim 64 Figure 4.19: Illustration of the displaced volume of water at MHWS caused by land claim 65 v Figure 4.20: Past and future land claim works in Singapore 68 Figure 4.21: Basic wet flood-proofing measures for a residential structure 70 Figure 4.22: Basic dry flood-proofing measures for a residential structure 71 Figure 4.23: Floating agriculture at Lake Inle, Burma 83 Figure 4.24: Flood hazard map for the area around Cairns, Australia 88 Figure 4.25: Flood hazard map of Montego Bay, Jamaica 91 Figure 4.26: Components of a flood warning system 93 Figure 4.27: Information flows in the Bangladesh CPP 100 Figure 4.28: The process of managed realignment 102 Figure 4.29: Effect of saltmarshes on required seawall standards and consequent costs 103 Figure 4.30: Types of coastal setback 110 Figure 4.31: Differing flood impacts after failure of structural defences and setbacks 111 Figure 4.32: Setback distances employed in Barbados 115 Figure 4.33: Contributing factors to the design water level and required crest height of a hard defence 118 Figure 4.34: Beach slopes and wave breaker types 119 List of Tables Table 4.1: Complementary and competing adaptation technologies 19 Table 4.2: Current degree of experience in the application of adaptation technologies 20 Table 4.3: Poole Bay beach nourishments 2005 – 2009 30 Table 4.4: History of erosion control measures, Bar Beach, Nigeria 45 Table 4.5: Overview of storm surge barriers, types and costs 58 Table 4.6: Costs of completed closure dams in Bangladesh 59 Table 4.7: Approximate costs of dry flood-proofing measures in the USA 73 Table 4.8: NFIP recommended flood-resistant materials 76 Table 4.9: Costs of implementing a floating agricultural system in Bangladesh 84 Table 4.10: Typical components of a flood warning, forecasting and emergency response process 94 Table 4.11: Bangladesh SWC warning message dissemination system 101 Table 4.12: Essential and secondary knowledge requirements for the 13 adaptation technologies discussed 116 Table 4.13: Potential sources of knowledge for the knowledge requirements outlined in Table 4.12 123 Table 4.14: Evaluative monitoring requirements for the 13 adaptation technologies discussed 126 Table 4.15: Specific tools and techniques used for monitoring adaptation options 130 Table 5.1: Potentially important criteria for determining effectiveness of coastal flood and erosion adaptation 134 vi Abbreviations AR4 IPCC 4th Assessment Report (published in 2007) BIS Beach Improvement Scheme BMD Bangladesh Meteorological Department CBA Cost-Benefit Analysis CDMP Caribbean Disaster Mitigation Project CEA Cost-Effectiveness Analysis CIDA Canadian International Development Agency CLIFFPLAN Numerical cliff erosion model (Meadowcroft et al., 1999) CPP Cyclone Preparedness Program (Bangladeshi national programme) dGPS Differential Global Positioning System FEMA US Federal Emergency Management Association GIS Geographic Information System GPS Global Positioning System HAT Highest Astronomical Tide ICZM Integrated Coastal Zone Management IPCC Intergovernmental Panel on Climate Change LiDAR Light Detection and Ranging (survey system) MCA Multi-Criteria Analysis MHW Mean High Water MHWM Mean High Water Mark MHWS Mean High Water Spring Tide MLW Mean Low Water MLWS Mean Low Water Spring Tide NAPA National Adaptation Programme of Action (a process for identifying priority activities for adapting to climate change in least developed countries, reported to the UNFCCC) NCC National Coordination Committee (Bangladeshi organisation) NFIP National Flood Insurance Programme (of FEMA) NGO Non-Governmental Organisation vii OAS Organization of American States (an international organisation including the 35 independent states of the Americas) RSLR Relative Sea Level Rise SCAPE Soft Cliff and Platform Erosion (numerical cliff erosion model; Walkden & Hall, 2005) SLR Sea Level Rise SPARRSO Space Research & Remote Sensing Organisation (Bangladeshi organisation) SST Sea Surface Temperature TAOS The Arbiter of Storms – Caribbean storm hazard model used in flood hazard mapping (Watson & Johnson, 1999) UNEP United Nations Environment Programme UNFCCC United Nations Framework Convention on Climate Change USAID US Agency for International Development USDA United States Department of Agriculture VAT Value Added Tax WMO World Meteorological Organisation WRDS Wetland Resource Development Society (voluntary research & development organisation) WWF World Wildlife Fund viii Preface Coastal zones in many parts of the world are densely populated centres of critical economic activity. Sea level rise and more intense storms, waves, and surges due to climate change pose a serious threat to large numbers of people living in these areas. Consequently many developing countries have identified coastal zones as a priority area for climate change adaptation. These countries, however, often need assistance to identify adaptation options, formulate adaptation strategies and plans, and implement adaptation measures that lower the risk and actual losses from climate change impacts.