Rooftop Rainwater Source Emission Reduction Mode Based On Design Of Sponge City

Nowadays,China is in the rapid development period of Urbanization.Water conservation natural ground has been replaced by a large amounts of impervious underlying surface with urbanization process,which has caused many problems such as urban waterlogging and water pollution.Meanwhile,under the background of the changeable global environment,the traditional "gray drainage facilities" is difficult to meet the needs of urban drainage.Severe urban waterlogging caused by the increase of hardened area,such as building roofs and urban roads,has been a serious social issue.Therefore,the central government has put forward the idea of "sponge city",in order to realize the control of rainwater runoff and the reduction of pollution load.Based on the idea,the paper studied the source emission reduction mode for rooftop rainwater.Firstly,the paper analyzed the status of urban waterlogging,water shortage and water pollution problems in China,and pointed out the contradiction between urban waterlogging and water resource shortage based on the read of literature.Then,the emission reduction mode of roof rainwater was designed based on the control of rainwater runoff on the roof of the building,consisting of the initial rainwater split-flow mode,the middle term rainwater storage and utilization mode and the later term rainwater recharge groundwater mode.Finally,physical model experiments were carried out to verify the emission reduction mode of roof rainwater.The main conclusions in this paper are as follows:(1)Focusing on serious pollution of roof initial rainwater,the initial rainwater split-flow mode,can realize initial rainwater split-flow and collection by using the pulley block principle,was designed.Then,the paper gave the running process and the shape and size of each part of the model.Model test results show that the concentration of TSS,COD,TP and TN in initial rainwater is higher mid-late rainwater,pollutant concentration in rainwater significantly reduces after initial rainwater split-flow process and proves the feasibility of the mode.(2)Designed middle term rainwater storage and utilization mode and the paper gave the running process and the structural feature of each part of the model.The model show up the good collection and storage rainwater effect,which provides relatively good rainwater for later-term recharge groundwater mode.(3)Designed the later term rainwater recharge groundwater mode to realize the local utilization of roof rainwater,and then gave the running process and the shape and size of model.Model test results show the feasibility of the mode and find that different embedded depths can lead to different groundwater recharge efficiency.The best efficiency of groundwater recharge is in loose soil with high porosity and shallow depth.The paper enriched the theory of urban rain flood utilization,which can provide technical reference for the planning and construction of "sponge city",and contribute to alleviate urban waterlogging,reduce rainwater runoff pollution and improve utilization of rainwater.