Optimization Of Drainage System In Waterlogging Area Based On LID

In recent years,the frequent flooding of domestic cities has seriously affected the life and production of residents and the development of national economy.There are two main reasons for this: one is that the development of urbanization makes the surface of the city harden and the surface permeability decreases,so that the rainfall runoff is larger and the flow time becomes shorter.The another is that the drainage system has been unable to withstand increasing drainage pressure due to the aging of the design standard and facilities in most cities of China.In order to reduce the pressure of urban drainage,China vigorously promoted the construction of sponge city.In the backdrop of the reality demand and the national policy,carrying out drainage optimization research in waterlogged areas is of great significance for rich scientific theory and engineering practice.This paper summarized the urban drainage system and research progress of sponge city at home and abroad.On the basis of this,this paper chose Taojiang county,Hunan province as the research object,and collected basic information related to hydrogeology,meteorological geography,underlying surface and current drainage facilities.Then it used MIKE URBAN to model the current drainage system of the research area,and analyzed the drainage capacity of the pipe network during different rainstorm.The simulation results showed that 38.5 percent of the pipe segment does not meet the rainstorm in one year,thus the drainage capacity of the pipeline network is an important factor leading to waterlogging.Secondly,this paper got the distribution of the overflow distribution of the node in the study area through the model to select the waterlogging point of the study area.By comparing the node overflow distribution and impervious rate distribution in the study area,we can find that node overflow is related to underlying surface impervious rate,overflow near nodes around sub catchment area of the numerous high impervious rate,and the greater the proportion of impervious,the greater the node flow capacity.Therefore,the high water permeability of the ground is another key factor leading to waterlogging.Based on the above analysis,this paper conducts research on the optimizationof drainage system in waterlogging area combining the research area cases from the following three aspects:Firstly,in response to the small and medium rainfall events,the paper puts forward the optimization scheme of adding LID measures to the urban drainage system.We improve the research area by studying the LID rainwater system control target decomposition method,construction technical route,LID facilities selection and layout method and so on,to get the LID in the study area rainwater system construction plan.Secondly,In order to solve the problem of excessive rainfall,the optimization scheme of urban large storage system was proposed.We have carried out the planning and transformation of the research area through the study of the selection of drainage and storage facilities of the city's surface,water system,reservoirs and wetlands,and obtained the construction plan of the urban large-scale storage system in the research area.Thirdly,Aiming at the standard range of rainfall events(in five years),the optimal scheme of drainage network system was proposed,and the effective connection between the LID rainwater system and the urban large scale storage system was realized.Finally,we once again by MIKE URBAN model to verify the effectiveness of the waterlogged sponge areas city scheme,simulation results show that after optimization and reconstruction,the study area flood point graveness,95% of the area can meet once every five years of rainfall return period.