孟加拉国沿海圩区全系统防洪标准探讨

11250 An Exploration of Systemwide FloodProtection Standards for Coastal Poldersin BangladeshPublic Disclosure Authorized Ruben JongejanMathijs van LeddenKasper LenderingJasper VerschuurDebashish Paul ShuvraBramka Arga JafinoSwarna Kazi Urban, Disaster Risk Management,Resilience and Land Global DepartmentNovember 2025 A verified reproducibility package for this paper isavailable athttp://reproducibility.worldbank.org,clickherefor direct access. Policy Research Working Paper11250 Abstract risk to US$18.6 billion investment cost + US$6.7 billionflood risk). This includes the substantial investment in bankprotection needed (~US$5 billion), irrespective of the floodprotection standards, to maintain the alignment of the pres-ent embankments around the coastal polders. Althoughthe absolute values of the economically optimal protectionlevels are subject to considerable uncertainty, a sensitivityanalysis confirms the robustness of the finding that there isconsiderable value in flood protection level differentiation.Flood protection standards are rarely based on economicconsiderations alone. They could also be informed by thedesire to reduce life safety risk or combat poverty. It isrecommended that the implications of applying differentperspectives on the tolerability of risks to determine differ-entiated flood protection standards be carefully explored inconsultation with stakeholders. Bangladesh has demonstrated how investment in coastalflood protection saves lives, reduces economic losses, andprotects development gains. Yet, its cost effectivenessdepends on the design standards, which are currentlyselected on a project-by-project basis. This is because atpresent, there is no law, policy, or agency guidance to guideor inform decisions on design standards for coastal poldersin the country. To inform the discussion on appropriateflood protection standards for Bangladesh’s coastal polders,this paper investigates what these standards would looklike if they were based on cost-benefit analyses. The analy-sis finds that implementing differentiated flood protectionstandards across the coastal polders can be a cost-effectivestrategy for further suppressing flood risks, reducing upto 27.5 percent of the total cost and flood risks (fromUS$23.4 billion investment cost + US$11 billion flood The Policy Research Working Paper Series disseminates the findings of work in progress to encourage the exchange of ideas about developmentissues. An objective of the series is to get the findings out quickly, even if the presentations are less than fully polished. The papers carry thenames of the authors and should be cited accordingly. The findings, interpretations, and conclusions expressed in this paper are entirely thoseof the authors. They do not necessarily represent the views of the International Bank for Reconstruction and Development/World Bank andits affiliated organizations, or those of the Executive Directors of the World Bank or the governments they represent. An Exploration of Systemwide Flood Protection Standards for CoastalPolders in Bangladesh Ruben Jongejan; The World BankMathijs van Ledden; The World BankKasper Lendering; The World BankJasper Verschuur; Delft University of TechnologyDebashish Paul Shuvra; The World BankBramka Arga Jafino; The World BankSwarna Kazi; The World Bank JEL Codes:Q54, O18, O21, O10Keywords: flood protection, resilience, disaster risk management, optimization, infrastructure planning Acknowledgments:We would like to thank Jolanta Kryspin-Watson, Jun Rentschler, and Dzung HuyNguyen for providing inputs and /or valuable comments that have helped improve this Working Paper. Thisresearch received financial support from the Japan-World Bank Program for Mainstreaming Disaster RiskManagement in Developing Countries, which is financed by the Government of Japan and receivedtechnical support from the World Bank Global Facility for Disaster Reduction and Recovery’s (GFDRR)Tokyo Disaster Risk Management Hub. 1.Introduction Bangladesh’s coastal zone comprises 139 polders,1housing a population that is expected to grow to 61million by 2050. Established in the 1960s, the polder system was originally designed to protect against tidalflooding and saline water intrusion, ensuring stable livelihoods, agricultural production, and local economicgrowth (Paul & Rashid, 2016). The Government of Bangladesh (GoB) has undertaken several large-scaleinitiatives to enhance the resilience of the coastal population. There has been a series of programs (e.g., theCoastal Embankment Project in the 1960s (Kais & Islam, 2023), the Coastal Embankment RehabilitationProject in the 1990s, and more recently, the Coastal Embankment Improvement Project - Phase I (CEIP-1)that just finished in 2024) to lower the risk of flooding in Bangladesh’s coastal zone. In these programs,infrastructure (e.g., embankments, drainage structures, etc.) has been built and rehabilitated to provideprotection against cyclone surges, river floods