Impacts of sea-level rise on groundwater inundation and river floods under changing climate

Rising sea levels increase coastal extreme events of inundation along the global coastlines. Existing hydrologic and groundwater models simulate inundation processes but simplify groundwater-surface water interactions, a key control on flood generation in coastal areas. Here we apply a coupled surface-subsurface hydrologic model to evaluate the sensitivity of shallow groundwater to sea-level rise across three watersheds in Southeast China. It was found that historical decrease of annual rainfall resulted in no changes in total water storage but lower streamflow. Sea-level rise can increase low flow and local groundwater inundation, without changes in total water storage. GIS analysis of elevation can give a first approximation of vulnerability to marine inundation. Our physics-based modeling approach helped capture the temporal dynamics of water table and improved process understanding on coastal flooding. This study provides a new insight to quantify the spatiotemporal dynamics of groundwater inundation and river floods across coastal watersheds.