A multi-dimensional framework for improving flood risk assessment: Application in the Han River Basin, China

Study region: The Han River Basin, China Study focus: As the water source of the Middle Route Project of the South to North Water Transfer Project, water security in the Han River Basin deeply impacts national water resource allocation. This study constructed a Multi-Dimensional Flood Risk Assessment (MDFRA) framework combining a comprehensive index system, an integrated weight method, and a clustering algorithm to assess flood risk in the Han River Basin. We first constructed a comprehensive index system including eight hazard indexes, four exposure indexes, and eight vulnerability indexes in demographic, economic, ecological, and infrastructural categories to assess flood risk. The index weights were determined by the integrated weight method, which integrated the Shapley value and the Analytic Hierarchy Process method (SAHP). Finally, the possibilistic fuzzy C-means algorithm was employed to identify flood risk levels. New hydrological insights for the region: The MDFRA framework presents flood risk in the Han River Basin realistically and comprehensively, revealing flood risk composition and providing more detailed risk information. Results show that high-risk regions accounted for 34.51% of the basin area and were mainly concentrated in the mid-lower reaches, while middle-risk (19.13%) and middle-high-risk (23.35%) regions were mainly distributed in the upstream. 4.52%, 5.12%, and 13.37% of the basin area were assigned as very-low, low, and middle-low risk regions respectively, and were mainly adjacent to the Danjiangkou reservoir. Flood-prone natural conditions and dense population and assets were the causes of high flood risk, while reservoir regulation and storage capacity had significantly alleviated flood risk.