Research On The Construction And Application Of Urban Flood Simulation Model

Flood and waterlogging disasters are the natural disasters with the highest frequency,heaviest losses,and widest impact in China.In recent years,urban rainstorm and waterlogging disasters have occurred frequently in China,and flood has become the most prominent water problem in cities.Therefore,further improving the level of urban flood simulation and prediction,predicting and predicting the risks of urban waterlogging disasters in advance,and providing timely warnings are urgent issues that need to be addressed in the prevention and management of urban flood disasters.The prediction and early warning of flood disasters cannot be separated from the support of models.In recent years,research on urban waterlogging warning has gained a lot of technical experience and achievements,providing strong support for urban flood control emergency management.However,currently in China,the prediction and prediction of flood disasters are mainly based on conceptual or empirical models.The physical concepts of the models are not clear,and they are severely affected by human activities and hydrological characteristics,requiring the intervention or correction of technical personnel.This makes the simulation and prediction of urban flood disasters by flood forecasting models not accurate enough.It is urgent to propose a flood simulation model suitable for urban waterlogging disasters,Improve simulation accuracy and timeliness.This article is based on the research progress and existing problems of flood models both domestically and internationally.Taking the Liang Shui River Basin in Beijing as an example,combined with the mechanism of urban flood production and concentration and the complex characteristics of real data,a coupled urban flood simulation model with physical mechanisms,including rainfall,runoff production,surface runoff,and pipeline network runoff models,is proposed.The simulation application and analysis are carried out,and the main research content and results are as follows.(1)A detailed introduction is given to the basic principles of urban underlying surface runoff generation model,drainage zoning network convergence,one-dimensional river network hydrodynamic model,and two-dimensional surface hydrodynamic model.Then,the coupling methods of each model are elaborated,providing technical support for constructing urban flood simulation models.(2)Based on the principles and methods of the urban hydrological and hydrodynamic coupling model mentioned above,a simulation model of urban flood in the Liangshui River Basin of Beijing is constructed by coupling the watershed runoff generation model,pipe network convergence model,river network convergence model,and surface overflow model.During the modeling process,the drainage units of the pipeline network were manually judged,and a total of 276 drainage units were divided,with an average area of 1.6969 million square meters;Based on this,combined with the distribution of inspection wells and rainwater pipelines,the entire research area was divided into 54318 catchment areas using the Tyson polygon method,with an average area of 58700 square meters per catchment area.Then,the rationality and reliability of the model are verified by comparing the simulation results with the measured data from the flood process and ponding conditions of the two typical rainstorm of "7.21" in 2012 and "7.20" in 2016 in Beijing.The results show that the average error between the simulated peak and the measured peak is 2.7% and 14% respectively,the peak time is basically the same,and the flood process simulation simulation has high accuracy.The errors in the depth of accumulated water are 17% and 35%,respectively.Considering that the depth of accumulated water is affected by uncertain factors such as terrain changes,drainage system operation status,and observation data accuracy,the simulation accuracy is basically satisfactory.(3)A total of 20 flood model simulation scenarios were set up in consideration of the rainstorm return period of the Liang Shui River basin,the boundary conditions of the downstream North Canal,Tonghui Henan flood diversion and other boundary conditions,to build a database of flood simulation scenarios in the Liang Shui River basin;Then,based on the simulation results of the flood and waterlogging model in the Liang Shui River basin,the risk account of the water accumulation points in the Liang Shui River basin under the 10-year design rainstorm scenario is established,and the information such as the catchment area,the maximum water accumulation depth,the water accumulation time,and the impact area of each water accumulation risk point is clear;(4)A model generalization was conducted for the approximately 1303 km long rainwater pipeline network within the Liang Shui River Basin.Based on the designed 1-year,3-year,5-year,and 10-year short duration rainfall processes,the actual load situation of the pipeline network was analyzed,and the actual drainage capacity of the pipeline network was evaluated.The comparison and analysis with the road design drainage standards were conducted,and the conclusion that most roads in the basin have insufficient drainage capacity was obtained,and the reasons were analyzed;Then,taking the Lize Bridge catchment area as an example,a flood model is constructed,Through multi scenario waterlogging simulation results,the main cause of waterlogging was analyzed,and it was found that the local terrain was concave.In addition,insufficient drainage capacity and the proportion of impermeable area on the underlying surface also have a significant impact on waterlogging and water accumulation,and the impact of river water level uplift on waterlogging was relatively small,And propose corresponding suggestions and measures for improving urban waterlogging.