How do sediment transport and deposition vary spatially and temporally in the southern Ganges-Brahmaputra-Meghna Delta?

Wednesday 18 November 2020 - 14:00 to 15:00
Virtual / VC
Dr Richard Hale, Old Dominion University, USA



The Sundarbans National Forest (SNF), located on the modern topset of the Ganges-Brahmaputra-Meghna (GBM) Delta, is the world’s largest mangrove stand (~10,000 km2), and provides a wide range of cultural, environmental, and economic benefits to the nation of Bangladesh. At present, sediment accretion in the SNF occurs at a rate comparable to that of the locally accelerated relative sea-level rise (~1.1 cm/yr), despite substantial modification of the regional sediment dynamics resulting from the construction of channel embankments. As ~50% of the sediment deposited in the SNF each year is recently delivered (<6 mos) from the GBM rivers, the threat of a reduction in sediment supply as a result of water and sediment diversions associated with India’s National River Linking Project raises concerns over the SNF’s continued sustainability. In this talk, we will examine: 1) how rates of sediment transport vary both spatially and seasonally in this tidally forced, monsoon impacted system, 2) the hydrodynamic conditions responsible for delivering sediment to the mangrove platform, where it accretes at a rate comparable to local effective sea-level rise. Using in situ measurements of water velocity and suspended sediment concentration, we document how transport conditions change with across a variety of spatial scales.  These observations are then compared to an existing dataset of platform deposition rates, allowing us to project impacts associated with a reduction in the sediment supplied to this region.

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