Simulation Of Urban Rainwater Management Based On Low Impact Development

Along with the acceleration of urbanization process,the city disease has appeared extreme increasingly.And global climate change leads to frequent occurrence of extreme weather.The humanistic environment and ecosystems have received the serious threat with the increase of surface runoff coefficient,total runoff and flood peak.Some important problems of rainwater utilization are put forward using scientific methods,which is especially important in effective rainwater management,recycling of the rain and sustainable development.The idea of Low Impact Development(LID)gets deeper into the hearts of the people in urban rainwater management in recent years.The remake of LID is an important key link of realizing sponge city development.In this paper,on the basis of predecessors’ research results,Sanba river baisn in Xuzhou was chosen as the planning area.The parameters of SWMM model was selected to simulate the precipitation and runoff characteristics under the condition of present situation in the city.Runoff regulation effec t was simulated using the LID of models.Technical support was provided to enhance the level of urban rainwater management,deepen the urban rainwater utilization and build livable,landscape,ecological city.The main research results are as follows:1)The SWMM model constructed,and basic property parameters extracted based on Arc GIS software platform.And as reference to comprehensive runoff coefficient,parameters of SWMM model was automatic calibrated and verified,which makes the model to meet the actual situation of the basin,and run the applicability and the rationality of the model.2)Quantitative and spatial change process of the parameters of hydrologic cycle and pipe network systemwas simulated in the scene of different rainfall and surface situation combined with the SWMM model.The results showed that:(1)Surface runoff,runoff coefficient all present the increasing trend(increase 49.03 mm,0.185),the parameters including overload,overflow and water level of junctions and conduits of the drainage pipe network increased significantly with the increase of rainfall return period.(2)In the same precipitation scene,Surface runoff increase 19.35%,runoff coefficient increase 0.08,overload and overflow of drainage junctions and conduits worse with the improvement of underlying surface impervious rate.(3)Spatially,high runoff coefficient,junctions of overload and overflow distributed in impermeable basin,upstream of Sanba river basin.Visibility,There are certain ability which controlled flood and drainage of the urban drainage system for small and moderate rain royal.However,there are unable to drain and manage the heavy storm rain flood safely,timely and effectively3)The core of urban stormwater management lies in the restoration of urban water circulation.the proportion of precipitation,runoff,infiltration and storage improved,and urban rainwater return to nature realized by the layout of different LID measures.Simulating the hydrological effect of LID based on SWMM model.The results show that(1)the reduction rate of surface runoff based on single LID measure decreased to about 2%inP=20a from 5.6% inP=0.5a,quantity,hours and runoff of overload and overflow of drainage junctions decreased,its regulation rate of overflow is as high as 78.01%(P=0.5a),which reduced to 13.51% with the increase of return period.(2)Under the comprehensive regulation of penetration pavement,green roofs and bio-retention cell,the overall runoff coefficient reduce 0.037,the surface water storage and surface runoff increased by 3.581 mm,3.225 mm.Visibility,there are regulating effects for urban rainfall based on LID measures,which can reduce surface runoff,a lleviate the pressure of the urban drainage pipe network.However,it’s worse for regulating rainstorm runoff.Hence,it is not good to solve the problems of urban rainfall management just rely on LID measures.4)As a node of the river basin,urban,its rainfall problems were dissolved reasonablely,we need overall considered multiple levels from nodes to lines to areas,from the perspective of the basin,the development of “sponge city” be realized.The results show that(1)The effect of modification based on LID in upstream for basin is better than downstream.Its storage capacity and infiltration quantity increased,and runoff coefficient reduced by 0.4-0.5,runoff coefficient reduced by 3-4% in downstream,ease laod of drainage pipe network.(2)The renewal and programming based on LID in the plaza,new,old communities make runoff coefficient respectively down from 0.781,0.377,0.641 to 0.175,0.157,0.287.and peak flow by the original lower to 0.08,0.04,0.07 m3/s.Visibility,Adjust measures to local conditions,it can restore betterly the natural characteristics of city Relieve urban surface runoff,and also create a beautiful,livable and green environment for people while designed rationally the measure and proportion of LID.