  The risk of extreme coastal flooding to Bangladesh's low-lying and densely
populated coastal regions, already vulnerable to tropical cyclones, remains
poorly quantified under a warming climate. Here, using a statistical-physical
downscaling approach, our projections under the IPCC SSP5-8.5 scenario show
that Bangladesh's 100-year coastal flood will likely intensify from 4.2m to
6.6m by the end of the twenty-first century. The Meghna-North Chattogram is the
most vulnerable region. The severity of coastal flooding season will broaden
significantly, amplifying the strongest during the late monsoon season.
Substantial increases are projected to seasonal coastal flood frequencies, with
a three-fold increase in back-to-back flooding events in the post-monsoon
season. The frequency of coastal flooding from destructive cyclones like Bhola
and Gorky will significantly increase by 13.3 and 19.8 times, respectively. Our
study heightens the urgency for attention and investment to enhance coastal
resilience and mitigate risk in Bangladesh.
