A Physics‐Based Approach to Project the Impact of Climate Change on Occurrence of Compound Floods in a Large River Delta

Abstract Climate change is intensifying compound flooding in coastal regions, caused by the co‐occurrence of coastal and fluvial floods. This trend increases the probability of disasters beyond historical precedent, posing growing threats to densely populated deltas. Existing studies, however, cannot fully characterize how a warming climate affects multiple flood drivers and their interactions, which may lead to biased projections of future compound extreme events. In this study, we develop a physics‐based method that dynamically integrates the impact of climate change on both tropical cyclone (TC) activities and rainfall‐runoff processes. We apply this method to project coastal‐fluvial compound flood risk in the Pearl River Delta (PRD). An ensemble of 100,000 storm events is generated to characterize possible compound extreme events under the historical (1974–2014) and future (2060–2100; SSP5‐8.5) climate scenarios. At a representative estuarine location, the projected results reveal a significant increase in the probability of coastal and fluvial extremes, with the return period decreasing from 55.5 to 15.5 years. These projections indicate that compound flood events unprecedented in the historical record are more likely to occur in the future. Our findings highlight the need for adaptive coastal hazard management strategies to address the escalating compound flood risk under climate change.