Post-surge recovery of coastal aquifers under climate change

Storm surge increases the salinity of coastal aquifers through subsequent vertical seawater intrusion. Climate change is expected to reduce the frequency of storm surges while increasing their intensity, raising complex challenges for the recovery of coastal aquifers to pre-surge conditions. Using integrated surface–subsurface numerical simulations of a generalized coastal aquifer, we examine how the shifts in storm-surge frequency and intensity control long-term salinization. The results show the emergence of two regimes: full recovery, where the aquifer returns to pre-surge conditions, and a shifted equilibrium, characterized by salt accumulation and reduced fresh groundwater availability. The transition between the regimes is captured by a dimensionless number E, linking recurrent storm-surge characteristics and aquifer properties to salt loading. This framework provides an efficient basis for assessing climate-change impacts on vulnerable coastal groundwater systems.