An Exploration of Systemwide Flood Protection Standards for Coastal Polders in Bangladesh

Bangladesh has demonstrated how investment in coastal flood protection saves lives, reduces economic losses, and protects development gains. Yet, its cost effectiveness depends on the design standards, which are currently selected on a project-by-project basis. This is because at present, there is no law, policy, or agency guidance to guide or inform decisions on design standards for coastal polders in the country. To inform the discussion on appropriate flood protection standards for Bangladesh’s coastal polders, this paper investigates what these standards would look like if they were based on cost-benefit analyses. The analysis finds that implementing differentiated flood protection standards across the coastal polders can be a cost-effective strategy for further suppressing flood risks, reducing up to 27.5 percent of the total cost and flood risks (from US$23.4 billion investment cost + US$11 billion flood risk to US$18.6 billion investment cost + US$6.7 billion flood risk). This includes the substantial investment in bank protection needed (~US$5 billion), irrespective of the flood protection standards, to maintain the alignment of the present embankments around the coastal polders. Although the absolute values of the economically optimal protection levels are subject to considerable uncertainty, a sensitivity analysis confirms the robustness of the finding that there is considerable value in flood protection level differentiation. Flood protection standards are rarely based on economic considerations alone. They could also be informed by the desire to reduce life safety risk or combat poverty. It is recommended that the implications of applying different perspectives on the tolerability of risks to determine differentiated flood protection standards be carefully explored in consultation with stakeholders.