Reproducibility package for An Exploration Of System-Wide Flood Protection Standards For Coastal Polders In Bangladesh

Bangladesh has demonstrated how investments in coastal flood protection save lives, reduce economic losses, and protect 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 Bangladesh. 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.

This study 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% of the total cost and flood risks (i.e., 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. Areas like Khulna (with significant economic activity and natural cyclone buffering from the Sundarbans) stand out as candidates for extra-high protection, because the cost to elevate defenses is relatively low while the benefits are substantial. While 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 are carefully explored in consultation with stakeholders.