Impacts of climate and land use change on hydrodynamics and sediment transport regime of the Ganga River Basin

Under climate change and pressure from human activities, extreme flood events are becoming a significant concern. The study involves setting up a coupled hydroclimate-hydrodynamic models over the Ganga River Basin by coupling the CORDEX regional climate models to the physically based Soil Water Assessment Tool-based hydrological model and MIKE 21C-based hydrodynamic model. The coupled model was employed to explore the flood inundation and dynamics of sediment mobilization amid various extreme events under future conditions. The water level, particularly for the 40-year return period for the late century (2061-2100), is estimated to rise in the future (0.9-1.2m). Since extreme streamflow has increased in the future, morphological transformations will also aggravate. Moreover, during the extreme events, the peaks in shear stress and velocity profile distribution have a propensity to coincide with the areas of the meander bend, implying that the river meander processes govern the shifts in the dynamics of the sediment transport. Additionally, the developed model framework has been employed to determine the areas affected and inundation pattern due to the 18 August 2008 flood in the Kosi River due to the embankment breach. Simulation exhibited that there is a good agreement between the simulated and observed inundation areas. Together with the evaluation of the susceptibility corresponding to lives and livelihoods, this information may facilitate decision-makers to develop ameliorative policies and adopt meaningful measures to alleviate the impacts.