Study On The Impact Of Changing Environment On Urban Runoff And Its Simulation Control

In recent years,urban rain and flood events caused by climate change and urbanization have occurred frequently,causing huge losses to the lives and property of the people.Carrying out research on the impact of changing environment on urban stormwater runoff will help to understand the causes and evolution of urban rainwater in essence and provide important technical support for minimizing the impact of urban rainwater.This article takes the urban area of Xi'an as the research object,uses data analysis and model simulation methods,explores the evolution of the changing environment and the characteristics of extreme precipitation changes,and clarifies the response mechanism of urban surface runoff to the changing environment.The process simulation analyzes the current conditions and the characteristics of urban rain and flood in the future changing environment,formulates different adaptation measures and evaluates the control effect of the measures,and forms a complete set of research systems on the formation,evolution and control of urban rain and flood,in order to scientifically respond to the future changing environment Provide basis for urban rain and flood.The main work and main conclusions made in this article are as follows:(1)Research on the evolution of changing environment and its impact on precipitation.Analyze the changing environmental evolution law from three aspects:the temperature change,the short-term extreme precipitation evolution law in the flood season and the urbanization evolution law.First,use the temperature data of Xi'an urban area to analyze the trend and sudden change of urban air temperature evolution.Then,based on the interpretation of remote sensing image data of Xi'an city from 1984 to 2017,the law of spatiotemporal evolution of urban expansion was explored.Finally,using the hourly precipitation data during the flood season in Xi'an city,the evolution of short-term extreme precipitation during the flood season is analyzed.The annual,flood season and four season average temperatures in Xi'an urban area all show a significant growth trend and abrupt changes,and the temperature increases significantly after the abrupt change.The extreme precipitation intensity and the frequency of extreme precipitation of different durations all showed an increasing trend,with a main cycle of 21 years of periodic alternating changes,and no obvious abrupt changes in the change trend.The area of cultivated land in the central urban area has decreased sharply,the area of construction land has expanded rapidly,and the intensity of land use has shifted from low-intensity land use to high-intensity land use.The urbanization process has a significant amplification effect on the intensity and frequency of short-term extreme precipitation.(2)Study on the influence of changing environment on urban surface runoff characteristics.Based on the rainfall-runoff model,taking Qujiang New District as the research object,the urban surface rainfall-runoff characteristics are analyzed by controlling the underlying surface and the change of rainfall input conditions.The expansion of the impervious area has a significant amplification effect on urban rainfall and runoff.The increase in rainfall has a linear amplification effect on runoff depth,flood peak flow,and runoff,and the most obvious amplification effect on the change range of the original high runoff depth.Rain peak Location is a key factor influencing the occurrence time of surface runoff peak flow.(3)Construction of Urban Rain and Flood Model and Simulation of Current Rain and Flood Process.According to the current underlying surface,elevation and rainwater pipe network conditions,an urban rainwater model was constructed,and the whole process of the urban rainwater flooding process,the formation of surface rainfall runoff,the flow of water in the rainwater pipe network,and the evolution of urban surface water flow were simulated and analyzed throughout the process.The model simulation errors are all within 10%,indicating that the model has good applicability in this area;the number of overflow nodes of the pipe network shows a nonlinear increase with the increase of the rainfall recurrence period;the proportion of the pipe network that drains under overload The rain recurrence period increased with the increase of the rain recurrence period from once in one year to once in 20 years.The proportion of pipeline load increased from 77.94%to 89.92%.The number of points increased with the increase of rainfall,and the area of accumulated water increased from 0.199 km2 to 3.194 km2.(4)Research on simulation and control of rain and flood process under future changing environment.Based on the results of the climate change model,the sequence of future rainfall events under A2,A1B,and B1 greenhouse gas emission scenarios is generated.The whole process simulates the urban rain and flood situation under the future change scenario.According to the actual situation,according to the principle of source reduction,process control,source reduction and process control,the combination of regulation measures of Plan A,Plan B,and Plan C was formulated respectively.Under different emission scenarios,the number of overflow nodes increased by 0.22%,0.89%,and 0%,respectively,and the length of overloaded pipelines increased by 0.14 km,0.86 km,and 0.14 km,respectively.The accumulated water area has increased by 0.416km,0.508km,and 0.336km respectively;the reduction rates of overflow nodes for different control schemes are 2.25%,35.33%,and 38.36%,respectively.The cut length of the overloaded pipeline network is 0km,10.55km,10.65km.Waterlogging area reduction is 0.406km2,0.012km2,0.873km2.The scheme based on gray-green coupling measures can effectively deal with the harm caused by the future changing environment to urban waterlogging.