Construction And Simulation Of Drainage Pipe Network Model Based On SWMM Model In A Feihe Area Of Hefei City

In recent years,with the continuous improvement of urbanization rate in China,the impervious rate of urban underlying surface has greatly increased,which led to the rainfall into the pipe network rapidly,and then changed the peak value and flow of urban rainfall runoff.In addition,the urban drainage network capacity did not match the urban development speed,which made urban waterlogging disasters frequently.Therefore,how to accurately simulate the change process of urban rainfall and solve the "focus" of the current pipe network has become an urgent problem to be solved.Based on this,this paper took Feihe District of Hefei City as the research object,and studied the drainage pipe network in this area through the combination of field investigation and model simulation.In this paper,SWMM software combined with Arc GIS technology was used to construct the urban rainwater and flood management model in Feihe area,and the empirical parameters in the model were calibrated by using the runoff coefficient method under the design rainstorm situation.Finally,the calibrated SWMM model was used to evaluate the capacity of the drainage pipe network in Feihe area of Hefei City and analyze the flood points.According to the analysis of current pipe network,and then put forward the concrete measures of optimization and transformation.The main research results of this paper were as follows:1.The operation principle of SWMM model was studied and analyzed,the requirements of SWMM model for input parameters were determined,and three kinds of LID control methods were analyzed.It provided a theoretical basis for the construction of drainage network model in Feihe area.2.Using the spatial analysis ability and data processing ability of Arc GIS software,the work of pipe network generalization and sub catchment division in the study area could be completed efficiently,and the required data in SWMM model could be obtained.Based on the rainfall data of Chicago rainfall pattern synthesis,the runoff coefficient method was used to calibrate 8 empirical parameters in SWMM model,including the maximum infiltration rate such as the maximum infiltration rate in SWMM model.The coefficient of variation of the parameters under the return period P = 0.5a,1a,2a,3a,5a,10 a was 5.24%,3.53%,3.46%,4.62%,7.2%,and 8.6% which indicated that this set of data was suitable for the study of urban flood model in the study area.3.The SWMM model was used to simulate the surface runoff and pipe network operation in different return periods（P = 0.5a ～ 10a）.The results showed that:（1）with the increase of the return period,the surface runoff increased from 14.644 mm at P = 0.5a to49.20 mm at P = 10 a,and the rainwater infiltration was basically stable at about 10.29 mm.It could be seen that with the increase of rainfall intensity,the infiltration amount in the study area is almost unchanged,it was proved that the soil permeability in the study area was not high.（2）In the study area,there are 33 pipes that did not meet the design rainfall and drainage standard of once every three years,accounting for only 7.7% of the whole study area;Under the 3-year design rainfall scenario,there were 13 nodes which are overloaded and overflow,accounting for only 3% of the whole study area.Therefore,the pipeline overload and node overflow in this area were not serious.Overload locations of pipes and joints were concentrated in the northwest and southernmost parts of the study area.（3）With increased of recurrence period,the peak runoff flow at the discharge outlet gradually increased,and the occurrence time of flood peak gradually advanced.Compared with 0.5years,the peak runoff of outlet 1 in the study area with returned periods of 1,2,3,5 and 10 years increased by 1.38 times,1.71 times,1.89 times,2.05 times and 2.19 times,and the peak time was also advanced by 1～11 minutes respectively.4.Through pipe network optimization and LID measures,the problem of overloading of pipe sections and nodes in the drainage pipe network system in the study area was solved.For the overloaded pipe section in the（Beijing Road-Tandu Road）section of the study area under the design rainfall of P=1a,the pipe diameter was enlarged to has increased the water passing capacity of the pipe network.After optimization,the pipe section of this section met the drainage requirements of the design rainfall of P=5a.It could guide the design of pipe network in urban flood control and drainage;According to the 8 sub-catchment areas with serious overflow at the well point in the design rainfall situation of P=3a,the sub-catchment areas were regulated and stored in the form of sunken green space in LID.The optimized sub-catchment areas could not only solve the problem of overflow at the well point,but also beautified the urban landscape.5.Based on the revelation of Henan heavy rain event,the waterlogging simulation of rare heavy rain（P= 50a）was carried out in the study area,and it was identified that there were 1 high-risk waterlogging point at the intersection of Longgang Road and Gan Tang Road,2 medium-risk waterlogging points at the intersection of Tangmo Road and Longchuan Road,and the intersection of Guangde Road and Gan Tang Road,respectively,which provided technical guidance for flood control work in the study area.Figure [37] table [25] reference [70]...