Morphological Evolution of Global River Deltas and Associated Flood Vulnerability

Close to half a billion people live in deltaic regions worldwide, including in a number of mega-cities. Deltaic regions act as central locations for agricultural production, livestock farming, fisheries and hydrocarbon extraction. Deltas are also biodiversity hotspots, and carry with them a vast cultural heritage. Over the past half century the frequency of high magnitude floods have increased, causing devastating socio-economic and ecological losses to human settlements and infrastructure in deltaic regions. The overarching goal of the study aims at providing perspectives on the drivers, mechanisms and trends of morphology changes and how these affect flood susceptibility in large deltas, globally.

This study aims at investigating the following research questions: (1) Are changes in fluvial sediment flux to the delta are directly linked to decadal changes in delta morphology? (2) Will the degradation of delta significantly increase flooding susceptibility? (3) How will trends of flood susceptibilities vary individually in the delta? (4) How much of a significant net increase in flood susceptibility can be expected through the 21^st century?

A multifaceted research approach combining (a) numerical modeling of riverine water and sediment fluxes, (b) remote sensing analysis of delta morphology changes and flooding dynamics, and (c) GIS analysis of socio-economic impacts of flooding on deltaic communities is performed. Numerical modeling is used to obtain fluvial sediment and water fluxes to deltas. Remote sensing techniques are used to map changes in deltaic topographic trends and flood inundation in the last four decades. These are combined, using GIS techniques, with geospatial land use and population distribution information, to quantify flooding impacts and their spatio-temporal dynamics. This study (1) elucidates the complex co-dependencies between riverine, deltaic and coastal mechanisms, (2) provides predictions for 21^st century dynamics, and (3) develops a numerical framework for future studies of these dynamics and their future trends.