Sea level rise and storm surge effects in a coastal heterogeneous aquifer: a 2D modelling study in northern Germany

Climate change will affect coastal groundwater resources due to the mean sea level rise (MSLR) and an increase in storm intensity and frequency. Increasing saltwater intrusion from the subsurface as well as intrusion into aquifers from land-surface storm surges can be expected. We numerically investigate the impacts of MSLR and storm surge events in a 2D cross-sectional aquifer at the North-German coast using the coupled surface-subsurface approach of the HydroGeoSphere model. Aquifer heterogeneity is considered to investigate the influence of heterogeneity on the migration of salt plumes in the aquifer. A 1 m MSLR causes the saltwater/freshwater interface to migrate up to 1250 m landward, and the salinized area of the aquifer to expand up to 2050 m landward. Results from a storm surge simulation show that salt plume fingers develop below the flooded land surface, however, the fate of the salt plumes is highly dependent on the hydraulic conductivity of the subsurface.