Mapping Coastal Flood Risk in China

Abstract Coastal flooding poses a significant threat to China’s coastal zones, driven by the combined effects of global climate change and rapid urbanization. However, owing to notable discrepancies in data accuracy, model construction, and parameter settings, the applicability of findings from existing regional studies is limited when extrapolated to broader macroscale risk assessments. Therefore, this study quantitatively assessed the risk of casualties and economic losses in China’s coastal areas under different return period scenarios using multi-source spatial data based on the LISFLOOD-FP hydraulic model with a fine 30-m spatial resolution. Extreme water levels corresponding to return periods of 20-, 50-, 100-, 200-, and 500-years estimated by historical observations from 65 tide-gauge stations were employed as boundary conditions to simulate the flood inundation. Taking inundation depth-damage curves into consideration, we subsequently quantified the spatial distribution of the population casualty rates and economic losses under different inundation scenarios. Our assessment results reveal pronounced spatial characteristics in coastal flood risk, with the most severe impacts concentrated in low-lying urban areas, such as the Bohai Rim regions, the Yangtze River Delta, and the Pearl River Delta. The results indicate that under the 500-year return period inundation scenario, the total flooded coastal area across 11 provinces reaches 20,983 km 2 , with the number of casualties amounting to 176,000 and economic losses totaling CNY 303.8 billion yuan (about USD 42.2 billion). The high-resolution flood risk maps developed in this study provide spatial information and data support for national-scale coastal management, disaster risk reduction, and land-use planning in China’s coastal areas.