Hydrometeorological-modeling-based analysis and risk assessment of a torrential rainfall flash flood in a data deficient area in Wenchuan County, Sichuan Province, China

The objective of this study is to simulate the rainfall-runoff process of mountain torrents in the Shou River Basin located in the southern part of Wenchuan County, Sichuan Province. The basin encountered a significant flood disaster on August 20, 2019, resulting in substantial human and economic losses, as well as limited hydrological data availability. This research employs a unidirectional coupling approach by integrating the Weather Research and Forecasting Model (WRF) with the Storm Water Management Model (SWMM) to accurately simulate rainfall-runoff processes. To account for the non-uniform distribution of precipitation within mountainous watersheds, high-precision rainfall data generated by WRF are extracted and utilized as input for the SWMM model. The quantitative comparison between the evolution of spatial distribution of rainstorms and hourly precipitation processes demonstrates that the WRF model effectively captures dynamic changes in rainstorms. Analysis results indicate a trend of rainfall center movement from midstream to downstream, with sub-watersheds' superimposed effect on rainfall response leading to increased flood peak response, duration, and destructive power. This study provides an effective method and reference for predicting and assessing mountain flood disasters in data-scarce areas such as the Shou River Basin.