Mechanisms of Seawater Intrusion Under Temporal Evolution of Geomorphology in Coastal Aquifers

Abstract Intertidal geomorphological evolution plays a vital role in coastal aquifer ecosystems. However, current studies on groundwater dynamics and water‐salt transport mainly focus on idealized linear or simplified irregular profiles. The poorly characterized mixing of saltwater and freshwater under evolving conditions has seriously constrained the development of effective wetland ecosystem restoration strategies. In this study, we combined laboratory experiments and numerical simulations to analyze how geomorphic changes influence water‐salt transport, characterize water‐salt distribution patterns during evolution, and emphasize the importance of temporal effects. Our findings reveal that, compared with the storm profile, the berm profile promote the development of a larger upper saline plume (USP) and more effectively suppresses the inland intrusion of the saltwater wedge (SW). During geomorphological evolution, while the beach profile may recover from a storm shape to a berm shape within a few months, the water‐salt system lags behind, exhibiting residual effects in the salinity field. The realignment of seawater infiltration zones and the persistence of salinity residuals lead to the transient coexistence of two USPs within the coastal aquifer, further enhancing water‐salt mixing. This study advances the understanding of dynamic water‐salt mixing mechanisms in coastal wetlands and guiding ecosystem restoration efforts.