Future Displacement Risk in Southeast Asia due to Coastal Flooding

Southeast Asia is particularly vulnerable to coastal flooding, with low-lying coastlines and high population densities converging to create significant exposure to sea-level rise and storm-induced floods. Here, we present a novel modelling framework for assessing displacement risk across coastal populations in Southeast Asia under various climate change scenarios.

Our approach builds on a newly developed global coastal flood model (Kasmalker et al., 2024) that accounts for both path-based attenuation and hydraulic connectivity, allowing for more realistic representations of flood extent than traditional “bathtub” methods. The model integrates future sea-level and tropical storm projections, capturing a range of potential flood scenarios up to 2100. We link the flooding model to an empirically calibrated displacement risk curve that translates housing damage into probable displacement outcomes. This risk curve, derived empirically from observational data, quantifies the likelihood of an individual or household being displacment given varying degrees of property loss or structural damage. The curve is then applied within a probabilistic risk assessment to compute both the average annual displacement (AAD) and the probable maximum displacement (PMD) across Southeast Asia’s coastal regions.

Our findings highlight significant spatial variability in displacement risk, influenced by regional differences in exposure, vulnerability, and projected climate impacts. Additionally, the probabilistic approach underscores the increasing probability of catastrophic flood events leading to large-scale, sudden-onset displacement. By identifying regional hotspots of high displacement risk, our study provides a critical tool for policymakers and stakeholders to prioritise coastal resilience investments and develop adaptation strategies for at-risk communities throughout Southeast Asia.