Significance in Numerical Simulation and Optimization Method Based on Multi-Indicator Sensitivity Analysis for Low Impact Development Practice Strategy

Evaluating the performance of sponge city practices under actual conditions is essential for managing urban stormwater. Existing studies in urban stormwater management have rarely employed numerical simulations to model hydrological processes under actual Three-Dimensional (3D) conditions. In this study, a numerical computational model is developed to simulate the hydrological processes and reveal the temporal and spatial variation of runoff in relation to impervious surfaces and concave herbaceous fields. The applicability of the 3D modules was evaluated using the Chicago rain pattern formula under three recurrence periods: precipitation within one, five, and ten years. The results indicate that the thickness and slope of planting soil are the most sensitive factors regarding sponge city performance, with comprehensive factors of 0.754 and 0.461. The optimal structural parameters of the concave herbaceous field were obtained as follows: aquifer height, 200 mm; planting soil thickness, 600 mm; planting soil slope, 1.5%; planting soil porosity, 0.45; overflow pipeline porosity, 0.3. The flood peak reduction rate, delay rate, and total runoff control rate were the best in a recurrence period of 5a, with 88.93%, 51.11%, and 78.76%, respectively. This study offers technical and conformed methodological support for simulating water quantity processes in sponge cities, and for the control of waterlogging and the recycling of runoff.