In order to explore the effectiveness of sponge facilities in flood control and analyze the correlation of surface inundation elements in sponge cities under heavy rainfall, this paper takes the Xihe Drainage Area in Jincheng City, Shanxi Province, as a case study. In comprehensive consideration of the runoff reduction benefits and construction cost-effectiveness of sponge facilities, the layout optimization of sponge facilities was conducted by using a multi-objective method. A hydrological and hydrodynamic coupling model was employed to simulate surface inundation characteristics and to construct a joint probability distribution of flood features under different scenarios. The research findings indicate that the runoff reduction effect of sponge facilities gradually decreases as the rainfall return period increases. When the construction cost of low-impact development measures is 411 million yuan,the runoff reduction rates for the rainfall return periods of 10,20, 50, and 100 years are 0.34,0.33,0.31, and 0.30, respectively. Under the same rainfall return period, the water depth-flow velocity joint risk rate shows a significantly nonlinear decreasing trend as the water depth and flow velocity increase. For a water depth of 0.4 m, with the rainfall return periods of 10,20, 50, and 100 years, and the corresponding flow velocities being lower than 0.36,0.39,0.46, and 0.49 m/s, respectively, the water depth-flow velocity joint risk rate is above 0.8. The water depth-flow velocity cooperative risk rate is generally lower than the joint risk rate, and high-risk areas are more concentrated in regions with low water depths and flow velocities. When the water depth reaches 0.4 m, the water depth-flow velocity cooperative risk rate changes with flow velocity from 0 to 0.34.