Hydraulic Evaluation Of Drainage Network Based On MIKE URBAN Model And The Effect Study Of Optimization Scheme

In recent years,with the accelerating process of urbanization in China,the proportion of hardened surfaces in urban areas has been increasing year by year,making it increasingly difficult for rainfall to naturally infiltrate the ground.Coupled with the impact of global warming,extreme rainfall events have become more frequent,resulting in an increasing number of occurrences and intensities of urban waterlogging disasters,which seriously affect the safety of people’s lives and property.At the same time,industrial parks,as an integral part of urban economic development,will suffer incalculable economic losses if they are frequently affected by waterlogging disasters in the long term.The drainage capacity of the drainage pipe network is a key factor affecting the occurrence of waterlogging,so it is necessary to evaluate,optimize,and improve the drainage capacity of the current pipe network system to ensure smooth urban drainage and effectively control waterlogging.Based on the above reasons,this study takes the West Industrial Park in Guixi,Jiangxi Province as the research object.Through constructing a MIKE URBAN model,the comprehensive evaluation of the drainage capacity of the current pipe network system in the study area is achieved.Based on the evaluation results,short-term emergency and long-term planning improvement proposals are proposed for the current surface and pipe network system.The optimization effects of different proposals are compared based on the flow rate of the pipe section,the network load,and the overflow situation of the nodes.The study provides important reference value for the improvement and optimization of the drainage system in the research area.The main research conclusions are as follows:(1)Based on collected basic data,a MIKE URBAN network model was constructed by generalizing the underlaying surface and drainage system in the study area.The model was calibrated and validated using measured rainfall data and monitored pipe flow data.The analysis showed that the model had good accuracy.(2)The design of rainfall boundary conditions was divided into two types:short-duration and long-duration.For short-duration rainfall(1h,2h,3h),five rainfall return periods(1a,3a,5a,10 a,and 20a)were selected,while for long-duration rainfall(24h),three rainfall return periods(10a,20 a,and 30a)were selected.Hydraulic simulations were performed for each scenario,and the analysis of the simulation results showed that the length of fully loaded pipe segments and the number of overflow nodes increased as the rainfall return period increased.Under short-duration rainfall(1h,2h,3h),the proportion of pipe segments that do not meet the minimum standard of the local planning regulations of Guixi City were 79.69%,76.37%,and 73.49%,respectively,and the proportion of overflow nodes were41.30%,39.13%,and 34.06%,respectively.Under long-duration rainfall(24h),the proportion of pipe segments that do not meet the 20-year return period standard were74.74%,and the proportion of overflow nodes were 44.20%.The data indicates that the overall drainage capacity of the study area is low,and corresponding improvement measures are urgently needed.(3)Based on the evaluation of the drainage system in the study area and the overflow situation at nodes,three improvement plans were designed.The first plan was a Low Impact Development(LID)plan,and the other two were combination plans that included additional drainage network improvements based on the LID plan.These two combination plans were divided into short-term emergency improvement plans and long-term planning improvement plans.Rainfall boundary conditions were selected for a 2-hour rainfall event with a return period of 5 and 20 years,as well as a24-hour rainfall event with a return period of 20 years.The results showed that the LID improvement plan had a low optimization effect,and the two combination plans with added drainage network improvements had a significant optimization effect.During the 2-hour short-term rainfall event,combination plan two showed a significant improvement in optimization effect compared to combination plan one when experiencing a 5-year return period rainfall event,but the improvement was lower during a 20-year return period rainfall event.During the 24-hour long-term rainfall event,combination plan two showed a lower improvement in reducing the length of full-flow pipe segments compared to combination plan one,but a significant increase in reducing the number of overflow nodes.