Modelling Multidecadal Fluvial Sediment Fluxes to Deltas Under Future Environmental Change

Abstract:

As low lying coastal regions deltas are prone to land loss, degradation, and flooding due to relative sea level rise. These processes endanger delta populations and infrastructure, a situation which is increasingly exacerbated by anthropogenic activities. The flux of fluvial sediment to deltas is a first order control on delta aggradation and thus the potential for the surface elevation of a delta to be maintained or rise relative to sea level. Aggradation may occur without anthropogenic interference, but it can also be induced by controlled flooding. This research investigates how future environmental changes through to 2100 will influence fluvial sediment delivery to a selection of 10 vulnerable deltas, thereby contributing to the understanding of relative sea level change projections for these fragile coastal systems.

The key environmental changes investigated in this study include anthropogenic climate change, reservoir construction, and land cover changes induced by changes in agricultural practices and vegetation cover. The effects of these environmental changes on fluvial sediment delivery are being evaluated using the catchment numerical model WBMsed, which is being calibrated for the selection of deltas using historical reference data. As a test case, the inputs for modelling current and future sediment fluxes to the Ganges-Brahmaputra-Meghna delta are refined using economic and population projections as proxies for anthropogenic influences on delta catchments.

This research will contribute to the prognosis for vulnerable deltas and inform their short- and long-term management by indicating the consequences of anthropogenic activities which affect delta elevation and sustainability via altering fluvial sediment processes. While this could give forewarning for the residents and managers of unsustainable deltas, it could also be used as an argument for or against various anthropogenic activities.