Degree

Doctor of Philosophy (PhD)

Department

Geology and Geophysics

Document Type

Dissertation

Abstract

The Ganges-Brahmaputra-Meghna (GBM) delta is one of the most hydrologically dynamic and densely populated regions in the world, and it is often considered one of the world’s most vulnerable deltas due to subsidence within embanked areas and sea-level rise. Thus, understanding the interaction of fluvial and tidal processes is of utmost importance as riverbank erosion and flooding pose a significant risk to millions of people that live on the GBM delta. To better assess the flood vulnerability throughout the GBM delta, we studied the geomorphology, sedimentology, and elevation dynamics of the fluvial-to-tidal transition zone (FTTZ) across Bangladesh. This project aims to (1) quantify the present and future flood risk throughout the FTTZ and (2) propose feasible solutions to alleviate flood risks.

The results show that embanked areas within the tidal deltaplain in the FTTZ in the southwest region of Bangladesh will experience a 67-200% increase in flood risk over the next 30 years. Embracing locally based solutions, we propose repurposing dredge spoils to elevate houses or embankments to lessen flood risk. In the more fluvial-active regions of the FTTZ, we determine that land loss to riverbank erosion is far more pronounced (>2X greater) in the upstream, fluvial-dominated regions as opposed to the downstream, tidal-dominated regions. While the tidal-dominated regions are less vulnerable to riverbank erosion, they are more vulnerable to flooding from storm surges associated with cyclones and sea-level rise. The results show that the tidal-dominated riverbanks are more stable due to a combination of mass extraction of sediments and duration of maximum water velocities. As the GBM delta is lacking extensive bathymetric, water level, and water velocity data, new data collection would further elucidate erosional and sedimentation patterns throughout the FTTZ.

Date

5-24-2022

Committee Chair

Wilson, Carol A.

Available for download on Wednesday, May 16, 2029

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