Mapping Flood Hazard Across Mainland China Through a Physics- Based Global Flood Model with Embedded Reservoir Operation Scheme

China’s diverse flood mechanisms, complex topography, and high population exposure make it highly vulnerable to flooding. Traditional indicator-based flood hazard assessments often lack the spatial and physics-based process fidelity needed to capture flood dynamics. Here, we use a hydrodynamics-driven Global Flood Model, CaMa-Flood (v4.2), incorporating reservoir operations, to refine national-scale flood hazard assessment for mainland China. Simulations forced with ECMWF ERA5-Reanalysis runoff demonstrate strong agreement with observed streamflow. Flood hazard maps at 0.05° resolution, based on modelled flood depths for multiple return periods, reveal that ~ 50% of mainland China is exposed to low to very high 1-in-100-year flood hazard, with 26% in high to very high hazard. Approximately 317 million hectares are in hazard-prone areas, notably in the Yangtze, Heilongjiang, Pearl, and Yellow river basins. High-risk zones coincide with major urban and economic centres Guangzhou, Nanjing, Wuhan and provinces such as Sichuan. The resulting maps provide useful information to support informed planning, resilience, and targeted mitigation strategies.