Study On Simulation Of Hydrological And Water Environmental Effects Of Sponge City Based On LID Reconstruction

With the acceleration of urbanization and the global climate change,many cities in China have experienced problems such as frequent rainstorms and waterlogging,and the deteriorating water quality of water bodies.The virtuous urban hydrological cycle and the sustainable development of the water environment have been seriously threatened.This paper takes the pilot project of Hengqin New Area of Zhuhai Sponge City as the research object,uses the model to simulate the low-impact development and construction,discusses its effect on the improvement of urban hydrology and water environment,and in view of the problems in the construction of sponge cities,explores different optimization measures of low-impact development in actual construction.The main conclusions are as follows:(1)The SWMM model of the study area was constructed,and the Morris method was used to explore the parameter sensitivity and its changing law,and the model was calibrated and verified.In terms of hydrology and hydraulics,the most sensitive parameters for total runoff and peak runoff are N-Imperv,followed by Roughness and N-Perv.In terms of water quality,road’s Exponent is the most sensitive to changes in pollution load and is positively correlated with it,roof’s Max Buildup and road’ Max Buildup are the most sensitive to changes in peak concentration and are positively correlated.After calibration and verification,it is shown that the model conforms to the actual hydrology and water environment and can be used for followup research.(2)The coupling model of SWMM and LISFLOOD-FP is used to simulate and study the hydrological and water environmental effects of LID in 2020.The hydrological effect simulation results show that: LID is beneficial to increase infiltration and depression,slowing down surface runoff,reducing overflow,total outflow and total runoff;LID construction effectively reduces the total runoff at the drainage outlet,and the reduction rate decreases with the increase of the return period;LID construction can slightly delay the discharge peak flow time of the outlet,and can effectively reduce the peak flow of the outlet.Two-dimensional surface inundation analysis shows that under different recurrence periods,LID construction in2020 can significantly reduce the submerged area with a water depth of 0.05～0.20 m,and can effectively slow down the growth rate of submergence.The simulation results of water environment effects show that the LID construction can effectively reduce the total load of various pollutants,and the peak reduction rate of TN and COD concentration is relatively high.In general,the construction of LID in 2020 will have a reduction effect on runoff,waterlogging and various pollutants.(3)Based on the actual construction status of the study area,discuss the optimization measures of LID measures from the three perspectives of combination type,area size,and layout location.For different combinations,Plan A(green roof,rain garden,permeable pavement)and Plan D(rain garden,permeable pavement,grass ditch)have the best control effects on total runoff,submerged area,waterlogging process,and pollutant load.For different areas,Plan RG＿20(20% area for LID transformation)has the best control effect on total runoff,submerged area,waterlogging process,and pollutant load.For different locations,the downstream plan(downstream of drainage system)has the best control effect on total runoff,submerged area and waterlogging process.