An integrated framework for evidence-based climate adaptation planning in water-related disaster management in Malwathu Oya Basin, Sri Lanka

Study region The Malwathu Oya basin, located in the dry zone of Sri Lanka, is highly vulnerable to hydroclimatic variability, experiencing recurrent floods during monsoon periods and water scarcity during dry periods. Study focus This study develops an integrated framework for risk-informed adaptation planning by linking multi-model climate projections, hydrological simulations, and socio-economic impact assessment. Climate projections characterize changes in rainfall variability and extremes and are incorporated into a seamless hydrological model to simulate basin-scale flow dynamics. Model outputs are coupled with depth–damage functions to estimate economic losses and population exposure under current and future conditions, and to evaluate adaptation strategies. New hydrological insights for the region Climate projections (2050–2075) indicate an overall increase in annual rainfall. This increase is characterized by greater temporal concentration and variability, leading to reduced discharges during dry months. Flood hazards are projected to intensify, with depths exceeding two meters and 30–40% expansion of inundation extent. Flood damages are expected to increase by 3–4 times for buildings, twofold for agriculture, with rural communities most vulnerable. Adaptation analysis shows that coordinated reservoir operations and crop diversification can effectively reduce multi-hazard risks. These findings highlight the importance of integrating climate, hydrological, and socio-economic processes to better represent basin-scale risks by providing a transferable framework for evidence-based adaptation planning and strengthening integrated water resources management (IWRM) in climate-vulnerable basins.