| In recent years,with the acceleration of urbanization,regional underlying surface conditions and rainfall characteristics have changed,resulting in frequent urban waterlogging disasters in China,causing serious impact on the lives and property safety of the people.In order to deal with the adverse effecte of urbanization,it is necessary to carry out a comprehensive and scientific simulation of urban rainwater drainage system,and combine the LID facilities to optimize and transform the current rainwater system to restore the hydrological mechanism under the natural state of the city as far as possible,so as to minimize the decline.loss due to low stormwater system risk.Based on the data of topography,pipe network and hydrology of the study area,a MIKE model is constructed to simulate the present situation of the study area,The regional hydrological effects under different recurrence period design rainfall scenarios are simulated and analyzed,and the risk of waterlogging is evaluated.Then,based on the analysis of the present situation,this paper studies the optimization transformation of rainwater drainage system and the change of drainage system in the study area,and analyzes the runoff efficiency and economic efficiency of each scheme,and finally obtains a set of green ecological rainwater system scheme in the study area".The main findings are as follows:(1)Based on the Mike Flood construction of the current rainwater system model in the study area,the impermeable coefficient,time step of 60s,initial loss of 0.0006,hydrological attenuation coefficient of 0.9m,Manning coefficient of 0.013 and surface confluence velocity of 0.3 m/s are determined by the measured rainfall verification of the rain flood model.The results show that the flow path line in the model has a high degree of coincidence with the measured values.(2)Using the model of One-dimensional rainwater pipe ntwork the study area,the drainage capacity of the current rainwater pipe network under different rainfall conditions was evaluated.The results showed that the total length of rainwater pipes in the study area was 26.39 km,More than 70%of the drainage capacity is less than once a year,the drainage capacity in 1.1.5 years was 3.1%,the drainage capacity in 1.5-3 years was 6.7%,and the drainage capacity in 3-5 years was 2.5%.The drainage capacity of rainwater pipe network system is relatively low.(3)Based on the Mike Flood coupling model,the risk analysis method of rainfall waterlogging based on the double index of inundation depth and water accumulation time is established,and four risk grades are divided into risk-free,low risk,middle risk and high risk-The areas with high risk and moderate risk of waterlogging are mainly distributed in Jincheng Road,Huaili West Road,Central Street,the periphery of Aviation Square and other main roads,white in the eastern region Xinghua Road,Nanguan Road,Huaili East Road,East Ring Road and other main roads have lower risk of rainwater drainage system due to better drainage capacity of pipe network.(4)When the total annual runoff control rate in the study area is determined tobe 85%,the designed rainfall corresponds to the rainfall process at 1.5 a h the recurrence period of the study area.Through the addition of LID facilities and the change of drainage system to optimize the rainwater system,a total of 1467607 LID facilities m2,1 closure well were designed.The green ecological rainwater system meets the requirement of 85%of the annual total runoff control rate,and the reduction rate of the total cumulative outflow of COD、TN、TP pollution load is 95%,80%,91%,and the comprehensive utilization ratio of the optimized scheme LID facilities has increased by 68%.The peak discharge of the cut-off shunt drainage system decreases.water volume change and peak occurrence time delay. |
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