<p>Semi-arid coastal basins are increasingly exposed to prolonged drought, intensive water use, and rapid land-use change, creating interacting climate and socio-environmental pressures. In this study, we integrate satellite remote sensing, hydroclimatic records, and socioeconomic data to assess how climate-related hazards and human responses interact in coastal basins of semi-arid central Chile during a ~ 15-year megadrought. We find that precipitation declined by 30–50% across the study area, while streamflow reductions exceeded 70% in some subbasins and groundwater levels declined by more than 100% relative to pre-megadrought conditions. Despite these conditions, agricultural vegetation indices remained relatively stable, indicating strong buffering through irrigation and increased groundwater reliance. In contrast, natural vegetation showed significant sensitivity to hydroclimatic variability with some buffering occurring in coastal forests that can obtain water from frequent fog events, and coastal lagoon systems exhibited non-linear responses, including prolonged disconnection from the ocean. These results reveal a cascading risk dynamic in which adaptation strategies in managed systems—particularly agriculture—mitigate local impacts but amplify hydrological stress downstream, contributing to groundwater depletion and ecosystem degradation. Our findings highlight the need to explicitly consider feedbacks between climate hazards, land use change, and water management when assessing adaptive capacity in semi-arid coastal basins, and provide an empirical basis for designing more integrated and sustainable adaptation pathways.</p>