Data scarcity is a significant obstacle to both flood simulation and flood risk analysis. This study used an Integrated Flood Modeling System (IFMS) to setup a 1D-2D coupled hydrodynamic model in order to simulate the flood inundation process in the Anning River Basin (ARB) in Sichuan Province under design flood scenarios with various return periods (5-year, 10-year, 20-year, 50-year, 100-year). Owing to the lack of available long-term time series data, we used the design flood flow of a hydrological station, design standard of levee engineering, and historical flooding events in order to validate the model. Then, the comprehensive risk degree ( R-value) method was used to elucidate the flood risk levels. Finally, we drew a flood risk map of the ARB and analyzed its flood risk. The statistical analysis produced the following findings: About 147.5 km ² of the total inundation areas in the ARB are inundated at an extremely high-risk level, and the inundation rate reached 75.18%. Among the key towns present, the percentage of extremely high-risk areas was greater than 80%. In terms of settlement flooding, the extremely high risk level had 184 inundation spots, which was much higher than the other risk categories. These results indicate that the risk of flooding in ARB is high. This study used hydrodynamic models with limited measured data in order to simulate flood inundation and assess the risk of riverine flooding. This study can serve as a reference for flood studies in similar rivers that lack measured hydrological data.