Abstract: Given the frequent occurrence of flood disasters in the middle and lower reaches of the Yangtze River Basin, this study aims to assess the inundation risk in specific cities by simulating basin rainfall and sub-catchment areas using the Tyson polygon method and river network density method. The SCS (Soil Conservation Service) model and local equal volume method are employed to simulate the submerged depth and range under different rainfall return periods. The results highlight that the primary flooded areas in the middle and lower reaches of the Yangtze River are concentrated in the low-lying regions of the Jianghan Plain, the Dongting Lake and Poyang Lake Plain, as well as the Yangtze River Delta. With the increase in the return period of rainfall, the area affected by flooding and the severity of land flooding intensifies. There is an approximate linear relationship between the amount of rainfall and the area of inundation. For each 1 mm increase in precipitation, the submerged area expands by 947 km² when the precipitation is below 80 mm/d and by 644 km² when it exceeds 80 mm/d. A specific analysis conducted at city level reveals that Wuhan, Nanjing, Nanchang, and Xiaogan face high risks and large scopes of inundation. Consequently, these cities require heightened attention and defense measures.

Key words: middle and lower reaches of the Yangtze River Basin, SCS model, local equal volume method, inundation analysis