| The rapid urbanization has changed the underlying surface infiltration capacity, coupled with frequent extreme rainfall events in recent years, which led to high concentration of pollutants carried by sharply increased runoff, urban flooding has occurred because of the limited capacity of traditional sewer pipeline, and pollutants threaten downstream ecological security. These issues highlight the drawbacks of traditional urban stormwater drainage concept. Learning from foreign Low Impact Development (Low Impact Development, LID) idea, combined with China's actual conditions, sponge city concept came into being. At present, China is in the pilot sponge cities construction period, related concepts and technology are still not perfect, whereas there are many LID controls (LIDs), how to evaluate various combined shcemes is an important issue need to be resolved. This study carried out sensitivity analysis of LIDs parameters and study assessment method of LIDs schemes under different scenarios, based on scenario driven and SWMM (Storm Water Management Model), in order to provide reference and support for sponge city, and urban drainage systems with LID.Runoff control modeling using SWMM with LID is one of efficient ways to build sponge city. The sensitivity analysis of input parameters in model was helpful to model practice. There are many literatures on sensitivity analysis of the SWMM hydrological, hydraulic and water quality modules, but few are on LID module. In this paper, the sensitivity analysis of input parameters of LIDs was carried out with the Morris method based on scenario driven strategy.The comprehensive cost-benefit evaluation system of LID was built from economic, social and environmental dimensions, and the fuzzy hierarchy comprehensive evaluation method with entropy weights was put forward. One area of Jiangnan Industry Zone, Chizhou city, Anhui province was selected as a case study, and the storm water sewer system model was set up based on SWMM According to the statistics of continuous many years daily rainfall and total annual runoff volume control ratio requirement, three different LID combination schemes for LID stormwater system were put forward through total control target area weight allocation. The first scheme includes bioretention cell, permeable pavement and green roof. The second was in combination of bioretention cell, permeable pavement and vegetative swale. The third was made up of rain garden, vegetative swale and green roof. Simulation results show that runoff reduction effects of three schemes are 80.6%,82.2% and 80.6% respectively, however, their costs, land use area and other benefits are not same.To make the decision assessment, the fuzzy hierarchy comprehensive evaluation method with entropy weights was employed to the three schemes. Before the assessment, the parameters of LIDs have been adjusted appropriately, and the final evaluation results show that the third scheme has the best comprehensive cost-benefit.Simulation analysis were conducted on traditional storm water system and LID stormwater system based on scenario driven for the impact of rainfall peak ratio (r) change of 2-year design storm, and the runoff control and peak attenuated effects under different rainfall intensity scenarios on both stormwater systems. Keeping average rainfall intensity unchanged, the runoff of traditional rainwater system's outfall decreases firstly and then increases with the increase of r, and runoff from LID stormwater system decreases. The outfall runoff peaks of both systems increase with r backwards. The runoff control effectiveness of LID stormwater system decreases with the increase of r, and the correlation exists in both peak flow attenuated effectiveness and precipitation where maximum peak reduction achieved with r=0.5. The simulation results show that the LID stormwater system perform the better effectiveness of attenuating peak flow and runoff under different design storm return periods with r= 0.5. |
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