Abstraction-barrier management of compound lateral–vertical saltwater intrusion under groundwater-pumping and storm-surge forcing in low-lying coastal aquifers 

<jats:p>Low-lying coastal aquifers are increasingly exposed to compound salinization pressures arising from groundwater pumping and storm-surge inundation. Groundwater abstraction promotes landward migration of the saline wedge, whereas storm surges introduce seawater through surface flooding and infiltration, generating vertically derived salinity that may persist long after inundation. Previous hydraulic- and abstraction-barrier studies have almost exclusively focused on pumping-induced lateral saltwater intrusion, while the effectiveness of such management interventions under concurrent lateral and vertical intrusion processes remains largely unexplored.This study investigates the performance of abstraction barriers for managing compound lateral–vertical saltwater intrusion in a low-lying coastal aquifer subjected to recurrent storm surges and groundwater pumping. A fully coupled surface–subsurface variable-density flow and transport model was used to simulate overland inundation, seawater infiltration, groundwater flow, and salinity redistribution. To the authors’ knowledge, this is the first study to evaluate abstraction-barrier performance within a compound intrusion framework that explicitly distinguishes pumping-induced lateral intrusion, storm-surge-driven vertical intrusion, and total aquifer salinization.The results show that abstraction barriers substantially restrict inland migration of the saline wedge, reduce overall salt accumulation, and improve groundwater quality at vulnerable production wells. However, management performance is pathway dependent. Configurations that strongly suppress lateral intrusion may simultaneously increase the persistence of storm-derived salinity within shallow and intermediate aquifer zones by altering post-event flushing and salinity redistribution processes. Consequently, reductions in total aquifer salinization do not necessarily correspond to faster recovery from storm-surge impacts.The findings demonstrate that management effectiveness under compound coastal hazards cannot be evaluated using conventional saltwater-intrusion indicators alone. Distinguishing lateral and vertical intrusion pathways provides a more robust basis for assessing abstraction-barrier performance and designing adaptive management strategies for storm-surge-affected coastal aquifers.</jats:p>