Global mapping of potential coastal compound flood risk at 0.1∘ resolution

Compound floods resulting from the concurrence of river overflow and elevated sea levels are becoming increasingly unpredictable as climate extremes intensify. However, most flood risk assessments still fail to account for the uncertainty in their co-occurrence. Here, we quantify potential coastal compound flood risk at 0.1∘ resolution by integrating flood hazard, population exposure, and empirical vulnerability. Specifically, we introduce a compound flood metric, which aggregates riverine and oceanic flood volumes across multiple return periods under a physically plausible co-occurrence assumption. We further derive an empirical vulnerability function based on the ratio between observed and maximum potential flood hazard. The results show that Asia exhibites the highest 35.22% internal high-risk grids, followed by Africa (20.21%), Europe (17.02%), South America (9.89%), and North America (2.31%), with river deltas and low-lying coasts emerging as global riskhotspots. Our study offers a conservative compound flood risk assessment under deep uncertainty, supporting more robust investment decisions. Major river deltas and low-lying coastal regions are susceptible to compound flood risk, according to a 0.1 degree grid scale conservative global assessment that evaluates the co occurrence of riverine and oceanic flooding, integrating flood hazard, population exposure, and empirical vulnerability.