Mapping future floods in coastal Bangladesh - Impacts of projected changes in sea level and precipitation

Sammanfattning: The exposure to flooding in coastal Bangladesh is expected to increase throughout the century as a result of climate change-induced sea level rise and intensified monsoon precipitation. The current consequences of flooding include damage to infrastructure, economy, and health through inundation and saline intrusion, and are likely to affect a larger population in the future. Adequate flood modelling using updated climate projections on a sub-national scale is thereby crucial to understand the impacts of climate change-induced flooding compared to today. The change in flood extent and depth by 2080 relative to 2010 has been modelled and mapped using CMIP6 climate projections of sea level rise and precipitation for the intermediate radiative forcing scenario SSP2-4.5, high SSP3-7.0, and very high SSP5-8.5, using both mean end extreme projections for each scenario. Precipitation-induced flooding was simulated using the triangular form-based multiple flow algorithm TFM-DYN, and coastal inundation at high tide was generated through a passive flood modelling approach that incorporates sea level rise, land subsidence, and tidal influence. The results are presented for a rural area in central coastal Bangladesh and suggest that both flood extent and depth are likely to increase across all SSP scenarios. Whilst smaller changes were observed for mean scenarios, the extreme scenarios resulted in the highest increase in flood extent and depth, where depth increased with higher magnitudes compared to extent. The findings highlight how floods in central coastal Bangladesh could become affected in a future climate, and can be considered for identification of flood-exposed areas.