Abstract: Extreme rainfall frequently triggers flash flood disasters, posing a threat to residents' lives and property. Understanding the spatial distribution of these disasters and their environmental precursors is crucial for disaster prevention. Using Sentinel-2 satellite imagery before and after the event, the dNDVI＜-0.1 criterion was applied to identify the spatial distribution of the "7·20" flash flood disaster in the Maliehe Basin of Hanyuan County, Sichuan in 2024. The environmental characteristics of the affected areas, including slope, aspect, relief, rainfall, and building distribution, were analyzed. The results indicate that the affected area covered 174.2 hm², with the extent of disaster in sub-basins positively correlated to their basin size. The main downstream sub-basin R7 had the largest affected area at 40.4 hm², followed by the tributary sub-basins B6, B7, and main subbasins R5 and R6. The median slope of the affected tributary sub-basins was around 20°, while severely affected sub-basins B6 and B7 had slopes of approximately 25° . In contrast, the affected main sub-basin R7 had a slope of about 15°, with the remaining sub-basins around 10°. Severely affected sub-basins exhibited greater relief, with tributary sub-basins B6 and B7 reaching 40 meters and the main sub-basin R7 reaching 25 meters. Rainfall distribution varied across the basins, with the average rainfall in tributary sub-basins B6, B7 and B8 exceeding 100 mm. In the main sub-basin R5, the damaged building area along the river reached 5 481.2 m², amplifying the disaster impact through river-adjacent structures. The findings systematically quantify the spatial distribution and environmental precursors of the "7·20" flash flood disaster in Hanyuan County, Sichuan, providing a reference for delineating flood-prone zones.