Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized Learning from Japan’s Experience inIntegratedUrbanFloodRisk Management: fromJapan’s Learning Knowledge Note 1: Assessing and Communicating UrbanFloodRisk andCommunicating Note1:Assessing Knowledge A Series of Knowledge Notes A Series ofKnowledge ©2019 The World Bank International Bank for Reconstruction and Development The World Bank Group 1818 H Street NW, Washington, DC 20433 USA October 2019 DISCLAIMER This work is a product of the staff of The World Bank with external contributions. 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. 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CITATION Please cite this series of knowledge notes and/or its individual elements as follows: World Bank. 2019. “Learning from Japan’s Experience in Integrated Urban Flood Risk Management: A Series of Knowledge Notes.” World Bank, Washington, D.C. World Bank. 2019. “Learning from Japan’s Experience in Integrated Urban Flood Risk Management: A Series of Knowledge Notes—Knowledge Note 1: Assessing and Communicating Urban Flood Risk.” World Bank, Washington, D.C. World Bank. 2019. “Learning from Japan’s Experience in Integrated Urban Flood Risk Management: A Series of Knowledge Notes—Knowledge Note 2: Planning and Prioritizing Urban Flood Risk Management Investments.” World Bank, Washington, D.C. World Bank. 2019. “Learning from Japan’s Experience in Integrated Urban Flood Risk Management: A Series of Knowledge Notes—Knowledge Note 3: Designing and Implementing Urban Flood Risk Management Investments.” World Bank, Washington, D.C. World Bank. 2019. “Learning from Japan’s Experience in Integrated Urban Flood Risk Management: A Series of Knowledge Notes—Knowledge Note 4: Operating and Maintaining Urban Flood Risk Management Investments.” World Bank, Washington, D.C. World Bank. 2019. “Learning from Japan’s Experience in Integrated Urban Flood Risk Management: A Series of Knowledge Notes—Appendix: Case Studies in Integrated Urban Flood Risk Management in Japan.” World Bank, Washington, D.C. Knowledge Note 1: Assessing and Communicating Urban Flood Risk i ACKNOWLEDGEMENTS The four-part series “Learning from Japan’s Experience in Integrated Urban Flood Risk Management: A Series of Knowledge Notes” was prepared by a World Bank team led by Jolanta Kryspin-Watson, and comprising Shoko Takemoto, Zuzana Stanton-Geddes, Kenya Endo, and Masatsugu Takamatsu. Primary and secondary data gathering, and research, was conducted by Washington CORE and Yachiyo Engineering Co., Ltd. The four reports benefited from additional research and contributions by Jia Wen Hoe, Sayaka Yoda, Toshihiro Sonoda, Alex Keeley, Tomoki Takebayashi, Thimali Thanuja Pathirana Batuwita Pathiranage, and Chinami Yamagami; and peer review by Vivien Deparday, Keiko Saito, Ryoji Takahashi, Bontje Marie Zangerling, Srinivasa Rao Podipireddy, Dixi Mengote-Quah, Dzung Huy Nguyen, and Camilo Lombana Cordoba. The team is also grateful for the support of Mika Iwasaki, Luis Tineo, Reiko Udagawa, and Haruko Nakamatsu. The Knowledge Notes were developed with valuable contributions and guidance from numerous Japanese professionals and experts on integrated urban flood risk management. These include Professor Hiroaki Furumai, the University of Tokyo; Arata Ichihashi, Tokyo Metropolitan Research Institute for Environmental Protection; Michiru Sasagawa, Rain City Support and People for Rainwater; Nobuyuki Tsuchiya, Japan Riverfront Research Center; Shinji Nishimura, Urban Renaissance Agency (UR); Keiji Takeda, UR; Mikio Ishiwatari, Japan International Cooperation Agency (JICA); Miki Inaoka, JICA; Tomoki Matsumura, Ministry of Land, Infrastructure, Transport and Tourism (MLIT); Akito Kinoshita, MLIT; Takuji Nakazato; Chikao Okuda, Tokyo Metropolitan Government; Professor Takanori Fukuoka, Tokyo University of Agriculture; Yorikazu Kitae, Development Bank of Japan (DBJ); Tomohiro Ishii, Yokohama City; Minato-Mirai 21 Promotion Division, Urban Development Bureau, Yokohama City; Environmental Planning Bureau, Yokohama City; and Shoji Takemoto, Kobe City. Editorial services were provided by Fayre Makeig and Lisa Ferraro Parmelee. Kenya Endo designed the report. The Knowledge Notes were prepared under the auspices of the Urban Floods Community of Practice (UFCOP). UFCOP is a global knowledge initiative led by the World Bank with support from the Global Facility for Disaster Reduction and Recovery (GFDRR) and others. The Knowledge Notes were developed with the financial support of the Japan–World Bank Program for Mainstreaming Disaster Risk Management in Developing Countries, which is financed by the Government of Japan and receives technical support from the World Bank Tokyo Disaster Risk Management Hub. Cover Image: Shiga Prefecture’s Disaster Information Map accessed from a smart phone. The map disseminates information on various natural disaster risks, including of floods, landslides, and earthquakes. The platform is used to enhance disaster risk awareness, preparedness, and evacuation and as a key urban flood risk management strategy. (Shiga Prefecture. n.d.[a]) Learning from Japan’s Experience in Integrated Urban Flood Risk Management Knowledge Note 1: Assessing and Communicating Urban Flood Risk ii Development of Knowledge Notes: The Japanese Experience in Integrated Urban Flood Risk Management Draft Knowledge Notes Knowledge Note 1: Urban Flood Risk Assessment and Risk Communication Table of Contents 1. Summary 1 2. Types of Urban Flood Risk 2 2.1 Urban Flood Risk in Japan 4 2.2 Risk Assessment and Communication Objectives/Stakeholders 6 3. Conducting Urban Flood Risk Assessments and Communicating Their Results 7 3.1 Japan’s Experience with Urban Flood Risk Assessments 7 Methodology 7 Informing the Design of Structural Flood Management Measures 10 Informing the Design of Nonstructural Flood Management Measures 13 Integrating Climate Change Considerations into Assessments of Urban Flood Risk 18 3.2 Japan’s Experience in Urban Flood Risk Communication 25 Enhancing Preparedness 25 4. Lessons Learned and Key Takeaways 30 5. References 32 Learning from Japan’s Experience in Integrated Urban Flood Risk Management Knowledge Note 1: Assessing and Communicating Urban Flood Risk iii List of Figures Figure 1. Diagram of Three Types of Urban Floods 3 Figure 2. Percentage of Capital, Population, and Land Area Located in Floodplains: Japan, the United Kingdom, and and the United States 5 Figure 3. Risks of Storm Surge in Japan’s Coastal Areas, by Type 5 Figure 4. The Process of Assessing River, Surface Water, and Storm Surge Flood Risk 10 Figure 5. Estimating Maximum Rainfall Considering the Effects of Climate Change 20 Figure 6. Regional Flood Risk Assessment, by Probable Maximum Precipitation Levels 21 List of Tables Table 1. Three Types of Urban Floods and Factors that Affect Their Risk 4 Table 2. Objectives of Risk Assessment and Risk Communication 6 Table 3. Common Risk Assessment Methods, Stakeholders, and Aims 7 Table 4. Classification of Rivers and Design Level of Flood Management Measures 10 Table 5. Approaches to Flood Risk Assessments with and without Climate Change Considerations 19 List of Boxes Box 1. A Storm Surge Flood Protection Park in Kagawa Prefecture: Assessing Risk to Enhance Storm Barriers 12 Figure B1.1: Takamatsu Port Shoreline before and after the Enhancement of the Seawall Box 2. Enhancing the Flood Preparedness of Ozu Memorial Hospital: Assessing Risk to Help Develop a Hazard Map Map and Business Continuity Plan 13 Figure B2.1: Inundation by the Hiji River in 1995 Figure B2.2: Installation of Flash Flood Barriers by Hospital Staff Box 3. Flood Evacuation Plans in Sanjo City: Assessing Risk to Improve Citizens’ Decision-Making Processes 15 Figure B3.1: Sanjo City’s Flood Risk Evacuation Map Box 4. Neighborhood Safety Maps in Shiga Prefecture: Using Risk Assessments to Raise Awareness 16 Figure B4.1: Flood Depth Map by Likely Frequency of Rainfall Level Box 5. Integrating Climate Change into Hazard Maps: Regional Evacuation Plans for Large-Scale Floods in Tokyo 23 Figure B5.1: Flood Hazard Maps for the Public: Projected Inundation Depth Map (above) and Inundation Duration Map (below) of Five Wards in Tokyo Box 6. Disseminating Flood Risk Information: The “Timeline” Method Used by Urban Railways 25 Box 7. Disseminating Key Information through Multiple Means: The Case of Tokyo Metro 26 Figure B7.1: Signboard Indicating the Elevation of the Station Entrance Compared with Sea Level Figure B7.2: Handy Safety Guide (Evacuation Handbook