Doomed to Drown? Sediment Dynamics, Infrastructure, and the Threat of Sea Level Rise in the Bengal Delta
Abstract
The Bengal Delta in Bangladesh is regularly described as a "delta in peril" of catastrophic coastal flooding. In order to maintain a positive surface elevation, sediment aggradation on the delta must be equal to or greater than that of local sea level rise. Paradoxically, widespread armoring of the delta by coastal embankments meant to protect crops from tidal flooding has limited fluvial floodplain deposition, leading to rapid compaction and lowered land surface levels. This renders the floodplains of the delta susceptible to devastating flooding by sea level rise and storm surges capable of breaching the poorly maintained embankments. The government of Bangladesh is currently considering a one-size-fits-all approach to renovating the embankments under the assumption that sediment dynamics in the delta are everywhere the same. However, natural physical processes are spatially variable across the delta front and therefore the impact of dikes on sediment dispersal and morphology should reflect these variations. Direct sedimentation measurements, short-lived radionuclides, and a simplified sediment routing model are used to show that transport processes and sedimentation rates are highly variable across the lower delta. Aggradation is more than double the rate of local sea level rise in some areas, and dominant modes of transport are reflected in the patterns of sediment routing and flux across the lower deltaplain, though embankments are major controls on sediment dynamics throughout the coastal delta. This challenges the assumption that the Bengal Delta is doomed to drown; rather it signifies that effective preparation for 21st century climate change requires consideration of spatially variable physical dynamics and local feedbacks with large-scale infrastructure.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFMGC14B..08R
- Keywords:
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- 0416 Biogeophysics;
- BIOGEOSCIENCES;
- 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCES;
- 1622 Earth system modeling;
- GLOBAL CHANGE;
- 1641 Sea level change;
- GLOBAL CHANGE