Degrees of hydrologic restoration by low impact development practices under different runoff volume capture goals

For urban stormwater management, the low impact development (LID) concept has been widely applied due to its perceived beneficial effects on restoring to the original hydrological cycle. Through both field monitoring and mathematical modeling, this research evaluated the combined effects of several LID measures, especially under heavy rainfall events that could otherwise have caused flooding problems. A pilot sponge-city project in China was evaluated as a case study. Comparison of hydrologic quantities among different scenarios under large storm events was made through modeling. The results demonstrated that the runoff volume capture ratio of the existing LID plan for the monitoring period is 97% and it can reduce the volume of runoff by 50.8–74.6%, reduce peak flow rate by 72.3–87.5% and extend the lag time by 12–30 min. If the volume capture ratio of annual rainfall goal of 80% is solely met, the resulting LID plan can't restore to the natural hydrology. In order to restore close to the original hydrological cycle, especially under the larger storm events, the volume capture ratio of annual rainfall should be set to 82% for the pilot project.