| At present,many cities in China suffered serious urban p ollution and non-point source pollution disasters.Studying the design structure of low im pact development(LID)measures and simulating the effectiveness of measures has important theoretical and practical value for solving floods and water pollution in urban areas of China.This study is based on the urban flood and non-point source pollution Mike Flood model and the LID single facility DRAINMOD model.The sponge pilot area and a certain area of Xi’an are used as research areas to study the regulation effect and the optimization of structural parameters of LID measures.The main conclusions are as follows:(1)In terms of regional-sc ale urban stormwater and non-point source pollution models,the Mike Flood model can take into account three aspects of hydrology,hydraulic and water quality when simulating the rain management measures.At the same time,when simulating the control effect of LID measures,the model can accurately describe the pre-development and post-development states of different land scenarios;the facilities-scale LID measures model,the DRAINMOD model is more meticulousness to nitrogen simulation,it is the widely used,(2)By simulating the regulation effect of LID measures under different recurrence periods in a pilot area of sponge.Under the condition that the total proportion of LID measures was 17.75%,compared with the traditional development mode,the overflow reduction rate was 22.4%～100%;the ratio of excess load pipe section was 0%～54.55%;the runoff reduction rate was 64.0%～81.52%.The load reduction rates of SS,COD,TN and TP were 19.20%-68.71%,19.19%～67.78%,18.72%-60.91%and 19.89%～68.75%,respectively.The average export concentration(EMC)reduction rates were 0.65%～42.07%,0.650%～40.34%,0.06%～27.62%and 1.51%～42.14%,respectively.At the same time,the LID measures also control the submerged range of the intrinsic point,that is,the submerged area on different submerged water depths and submerged periods were reduced by 11.11%～100%and 32.23%～100%,respectively.(3)Through the analyze of the change of water quantity and water quality in the study area with or without rain garden under different recurrence periods,the risk classification and assessment of intrinsic risk were carried out.In the case of a total proportion of rain gardens of 2%,after the addition of rain garden,the overflow reduction rate was 6.74%～65.23%;the ratio of excess load pipe section is 0%～11.15%;the runoff reduction rate was 1.93%～9.69%.The peak concentration reduction rates of SS,COD,TN and TP were 0.42%～1.08%,0.25%～0.93 8%,0.15%～0.65%and 0%～1,07%,respectively.The lo ad reduction rates were 2.3 6%～3 0.3 5%,2.37%～30.11%,2.3 4%～30.08%and 2.3 2%～31.35%,respectively.The submerged area on different submerged water depths and submerged periods were reduced by 0.30%～64.1 8%and 7.12%～100%,respectively.(4)The simulation studied the design parameters of the rain garden on the hydrological effect of the rain garden and optimized the parameters.When the aquifer depth is 20～30cm,the total annual runoff reduction rate of rainwater garden is increased by 10.75%～11.98%;the load reduction rates of NO3-N and NH3-N are increased by 16.52%～1 8.65%and 3.69%～5.44%,respectively.When the depth of the packing layer is 10～100cm,the load reduction rates of NO3-N and NH3-N are increased by 6.96%～15.35%and 2.16%～4.30%,respectively.If the modified filler 60%planting soil+30%and+ 5%sawdust+ 5%water plant sludge(WTR)is used as artificial filler,the corresponding filler layer thickness can be as small as 22 cm,and the traditional filler is planted soil,The corresponding filler layer has a thickness of 47 cm;if the requirements of 25 cm<soil thickness<120 cm and runoff reduction rate of 80%to 85%are satisfied,the modified filler rain garden can handle the incoming water of the six combinations.The traditional filler rain garden can handle five combinations. |
