Research On The Effect Of Pingxiang Spong City Based On The Swmm Model

With the development of urbanization,a large area of permeable surface is replaced by impermeable pavement,resulting in frequent urban waterlogging disasters and increasingly serious water pollution.In this context,in 2015,China put forward the construction concept of"sponge city",which aims to control the total amount of runoff,flood peak discharge and total amount of pollutants.According to the sponge urban concept guidance,this article from the perspective of sponge city,valuable in pingxiang city district as the research object,has constructed the study area of SWMM model,in 1a,3 a,5 a,10 a,15 a,20 a,30 a seven simulated under different rainfall return period and analyzes the research area LID control measures on runoff control effect,and with the traditional development mode of the simulation results were analyzed.This paper verifies whether the benefit of sponge city construction achieves the design goal and provides the theoretical basis and data support for the construction of sponge city in pingxiang.The main research results of this paper are as follows:(1)reasonably generalize the sub-catchment area and rainwater pipe network in the study area,construct the SWMM model in the study area,and set the model parameters.According to the formula of rainstorm intensity in pingxiang,the rainfall in different recurrence periods in the study area was quantified.The comprehensive runoff coefficient was taken as the objective function of model parameter calibration,and the rainstorm in different recurrence periods was simulated and verified.It was verified that the comprehensive runoff coefficient was all within the value range(0.56~0.73)of the actual comprehensive runoff coefficient of the city.Therefore,it is considered that the model parameters are reasonable and the simulation results can reflect the actual situation of rainfall and runoff in the study area.Finally,an example is given to verify the reliability of the model;(2)under the traditional development mode,when the rainfall recurrence period increased from 1a to 30a,the rainfall,runoff and peak flow increased by 2.15,2.38 and1.74 times,the total infiltration increased by 3.85%,the number of overflow nodes increased from 7 to 19,and the total overflow increased from 4.845m~3to 40.26m~3.The total load of suspended solids(SS),chemical oxygen demand(COD),total nitrogen(TN)and total phosphorus(TP)increased by 8.79%,17.32%,11.83%and 7.28%,respectively.It can be seen that with the increase of recurrence period,the total runoff,peak discharge,total pollutant load,number of overflow nodes and total overflow flow increased significantly;(3)compared with the traditional development mode,under the recurrence period of 1a and under the control of LID measures,the reduction rates of total runoff and peak flow in the study area were 84.5%and 99%,respectively,and the reduction rates of total load of pollutants SS,COD,TN and TP were 55.27%,59.26%,62.34%and 60.54%,respectively,and the reduction rates increased with the increase of recurrence period.The infiltration rate increased by 28.45mm,the number of overflow flow and overflow nodes decreased by 100%(7),the infiltration rate increased by 66.47mm and the number of overflow flow and overflow nodes decreased by 99.5%(18)under the recurrence period of 30a.It can be seen that LID control measures can not only reduce the pressure of drainage system in the community and reduce the risk of waterlogging,but also play a role in purifying water quality and making rainwater resource utilization;(4)hierarchy structure model is established by using analytic hierarchy process(ahp),to calculate the weights of every index,through fuzzy comprehensive evaluation method to calculate the LID measures control effect have to 87.3 points,said LID measures to control effect is good,the evaluation level for ?.