Study On Urban Flooding Under Design And Reai-time Simulation Condition Based On Radar Estimation And Forcast Of Rainfall

In recent years,with the accelerating process of urbanization,the extreme weather continues to occur,especially frequent occurrence of urban flooding disasters caused by heavy rain,it has seriously threatened personal safety,economic construction,etc.The study of urban flooding has gradually become the focus of research in water conservancy and municipal departments,the application of modelling technology to construct urban stormwater pipe network systems and the simulation of the formation process and submergence of urban flooding is an important method for studying urban flooding.Through simulating the process of runoff and confluence of urban surface and confluence of pipe network,it is possible to accurately determine the easy points of the drainage system,thus providing scientific basis for the planning of the pipeline network,stormwater management,post-disaster assessment and so on.The research on urban flooding simulation is mainly discussed from two aspects.One is based on the urban flooding simulation under the design conditions,and the other is based on the simulation under real-time conditions.The main difference between the two simulation methods is the input of rainfall,the former uses the rainfall of different scenarios(rainfall intensity of different return periods)as the model input,while the latter uses real-time rainfall as the input of the pipe network.Regardless of the simulation under design conditions or real-time simulation,rainfall is a necessary condition for model simulation,the accuracy of rainfll directly affects the accuracy of the simulation,however,most of the rainfall currently used in the simulation is input in the form of a point rainfall process,although the method can accurately obtain the rainfall value at a certain point,but with the continuous expansion of the study area,the uneven spatial distribution of rainfall shows more and more obvious,so it is imprecise to use a single rainfall value as the input of urban flooding research,for this reason,many scholars at home and abroad have proposed using surface rainfall instead of the point rainfall process as an input condition for flooding simulation,but the accuracy of rainfall calculated by these methods depends on the distribution of rainfall stations,it has certain limitations for the calculation of regional rainfall distribution.At the same time,the most critical point for real-time simulation is the need for a long enough forecast period,real-time simulation of the pipe network system using the real-time data measured by the rainfall station network can obtain a certain forecast period,but for the change in the underlying surface,the time of runoff and convergence turn shorter,which greatly shortens the forcast period.In this paper,aiming at the accuracy problem of rainfall input in the urban flooding simulation,using a single rainfall station design rainfall as input to improve the rainfall accuracy of the traditional simulation method,and to compensate the defect the traditional single point rainfall input,using radar estimation technology to calculate the spatial distribution of rainfall,and the spatial distribution of design rainfall in different return periods is deduced,for the problem of forecast period of real-time simulation,radar forcast technology was used to predict future rainfall,and combining the urban flooding model to real-time simulate and forecast,thus,the flooding disasters in the future was obtained.The main research results are as follows:(1)This paper proposes the idea of designing scenario simulation and real-time simulation of flooding disasters based on the combination of radar spatial distribution forecasting,future rainfall prediction and urban drainage network model.This paper introduces the simulation methods of urban flooding simulation in china,analyzes the inadequacy of rainfall as input in the method,the necessity of inputting rainfall spatial distribution in a model,and the forecast period of real-time simulation of flooding.(2)This paper optimized the hydro-frequency parameters and rainstorm intensity formula in the process of the traditional rain type.Through optimation,the error of hydrological frequency parameters and rainstorm intensity formula were reduce.(3)A method to design rainfall process suface was proposed,combining with the technology of quantitative estimation of spatial rainfall by radar.Tyson polygon,anti-distance weight space rainfall interpolation method were studied and their advantages and disadvantages were compared,and verified by examples.(4)The paper put forwarded a method to derive designing surface rainfall process.Based on the traditional design rainfall rainfall and the technology of radar quantitative estimation of spatial rainfall,according to the radar data,the typical rainfall was selected and design surface rainfall process of different return periods was ascertained.At the same time,the input method and simulation method of gridded spatial rainfall in the flooding model were studied.(5)A method combining radar extrapolation,quantitative rainfall estimation and hydraulic model was proposed.and the simulation experiment proves that the forecast period has greatly improved,comparing with the traditional based rainfallstations real-time simulation method.