Research And Application Of Sponge Measures In Key Urban Areas Based On SWMM

With the growth of population and the rapid development of economy,the global urbanization rate continues to improve,the city scale continues to expand,followed by urban waterlogging problem has become increasingly prominent,urban flood disaster has become an important problem of urban development.Combined with the concept of low impact development abroad,China puts forward the construction of "sponge city",which realizes the control of rainfall runoff process,purification of surface runoff quality and utilization of water resources by means of "infiltration,retention,storage,purification,utilization and drainage".In view of the above situation,this paper selects an urban area of Xining City as the research object,establishes a rainwater drainage system model based on SWMM,and explores the impact of LID measures,rainwater storage facilities and pipe network transformation on pipe network load,runoff and water quality under different return periods of rainfall.The main achievements are as follows:(1)The SWMM model of the rainwater drainage system in the study area is constructed,and the Nash efficiency coefficient between the simulated water volume and the measured water volume is used to verify the model,which proves that the model has good accuracy and good applicability in the study area.The study area is divided into 19 drainage areas,and LID measures are separately arranged for each drainage area according to the low impact development index.Finally,the total annual runoff control rate of the study area reaches 85.7%,which meets the requirements of the technical guidelines for sponge city construction.(2)After LID measures are loaded into the model,the reduction rate of overload pipe section is 41.7% ～ 78.6%,and the reduction rate of node overflow volume is52.9% ～ 70.3% under different return period rainfall conditions;the flood volume and flood peak of seven typical outlets are significantly reduced,the reduction rate of flood volume is about 46.0% ～ 68.2%,and the reduction rate of flood peak is about 17.7% ～53.7%.With the increase of rainfall return period,the reduction rate of overload pipe section,node overflow volume,flood volume and flood peak all decrease,and the reduction effect of flood peak is poor under heavy rainfall.(3)With the increase of rainfall return period,the total amount of pollutants in runoff increases with the increase of scour effect.The effect of LID measures on pollutant reduction is obvious,the reduction rate is about 60.3%-85.2%,and the reduction rate of pollutants decreases with the increase of design rainfall return period;With the increase of soil layer thickness in LID measures,runoff and infiltration in the process of rainfall will decrease in varying degrees,and water storage capacity will increase significantly,it shows that soil layer is an important factor to increase surface water storage in lid measures,the change of storage layer thickness in LID measures has little effect on runoff process;The results show that the rainwater storage facilities have obvious effect on runoff process control and pollutant reduction,and the effect on delaying flood peak is the most obvious under the condition of low rainfall.In conclusion,the simulation model based on SWMM shows that sponge measures have obvious control effect on the water quantity and water quality of rainfall runoff in the study area,which provides reference for the construction of sponge city in the research area.