Simulation Study On The Regulation Of Low Impact Development Measures On Runoff Based On SWMM

The rapid development of the city has increasing the water permeable area,reducing the infiltration amount,increasing the flow of production,changing the process of the natural hydrological cycle,resulting in the intensification of the flood and waterlogging disasters.The traditional treatment of rainwater by platoon led to a large amount of rainwater being drained away.The increase of population density caused the increase of water demand of urban units and led to the strain of water resources.Under such circumstances,it is particularly important to reduce the impact of urbanization on the hydrological cycle,so that more water stagnation can be stored in the city and serve the urban environment and construction.The construction of the sponge city is through various kinds of ecological facilities,so that the hydrological characteristics after the development and construction of the city are as close to the development and construction as possible,and the low impact development is the requirement of the construction of the sponge city.Taking the campus of Agricultural University of Hebei in Baoding as the research area,this paper establishes a hydrological model under the current situation of the study area through the Storm Water Management Model(SWMM).The model parameters are determined and the model is tested by using the rainfall runoff process in five different regions and the fitting degree of the model simulated runoff process.The Nash-Sutcliffe efficiency coefficient,the relative error of peak flow rate and the absolute error of peak time are used to reflect the accuracy of model parameter rate determination and model verification,and the effects of different rainfall recurrence periods(0.5a,1a,2a,5a,10a)on the current runoff in the study area are quantitatively analyzed.The results show that:The Nash-Sutcliffe efficiency coefficient of the flow rate during the parameter rate period and the model verification is more than 0.8,the relative error of the flood peak flow is less than 16%,and the absolute error of the peak time is within 2min,which indicates that the simulated runoff process is in good agreement with the actual monitoring process;under the rainfall conditions of different recurrence periods(0.5a,1a,2a,5a,10a),the runoff coefficient and runoff coefficient are lower than that in the study area when adding various LID technical measures and their measures.The current runoff peak value of the study area is 30%-15%,and the total runoff changes in the study area.The rate is48%-44%,the peak time lag 10-1min;the current runoff peak change rate of the lower concave green space is 19%-5%,the total runoff total change rate is 22%-17%,the peak time lag 5-0min,the current runoff peak change rate of the research area is 25%-9%,thetotal runoff total change rate is 29%-24%,the peak time lag 7-1min;Under the combination of the three measures,the peak runoff rate in the study area is 66%-45%,the total runoff change rate is 79%-75%,and the peak time is 20-5min.All of them indicate that the current runoff in the study area has been reduced and retained;Comparison analysis under the present situation in the study area,add the permeable pavement,recessed green space,the rain barrel and three measures under the combination of process of runoff,runoff coefficient,as well as a variety of solutions about the present situation of the study area under the peak runoff reduction rate and total runoff reduction rate.The research shows that the combination of the three measures is most obvious in regulating the current runoff in the study area,followed by permeable pavement,rainwater bucket and concave green space.With the decrease of rainfall frequency,the reduction effect and retention effect on runoff are reduced by any kind of measure.The combination of LID measures realizes the source control and process control of the current runoff in the study area,thus reducing the drainage burden of the drainage pipe network.