Research of storm flood regulation efficiency of the low impact development of exogenous-rainwater park based on the SWMM simulation.

Compared with other urban construction area, the park area has large well-drained underlying surface, which can work with the city pipe network to accept more exogenous rainwater and regulate the storm flood. This study generalizes the research area and constructs the low impact development (LID) model and traditional development model through a case study of Binhu East Road Park in Qianan City. The research introduces the exogenous rainwater and applies the storm water management model (SWMM) in 1 hour rainfall event with different return periods (once every 1, 2, 5, 10 and 20 years), simulating the regulative effect of two development models in total runoff, peak flow as well as time of peak flow appearance and the control efficiency of single LID facility under once 2-year 1 hour rainfall event. The results show that:1) The SWMM model can stimulate the LID facilities' regulation of rainwater, and provide the technical supports and theory evidences for urban construction. 2) When setting goals of runoff regulation, we should plan the catchment sizes of exogenous-rainwater combined with the site current situation. 3) LID model has a good effect on storm flood regulation, can decrease the total runoff, peak flow and delay the time of peak flow occurrence significantly. Under the rainfall return periods from 1 to 20 years, the park construction based on the LID model can reduce total runoff, and peak flow by 100%-37.69% and 100%-40.55%, and eliminate the peak flow or delay the time of peak flow occurrence by 135-24 min, respectively. The efficiency of LID facilities decreasing total runoff ranked as: rain garden＞combined system＞vegetative swale＞bio-retention cell＞permeable pavement. The efficiency of LID facilities decreasing peak flow ranked as: rain garden＞combined system＞bio-retention cell＞vegetative swale＞permeable pavement. The efficiency of LID facilities to postpone the time of peak flow occurrence ranked as: combined system＞rain garden＞bio-retention cell＞vegetative swale＞permeable pavement. 4) When designing a low impact development park, we should consider other functional requirements such as disaster prevention.