Research On The Simulation And Prediction Of Urban Flooding In Nantai Island Of Fuzhou

In recent years,urban flooding disasters have occurred frequently in most cities in my country,which has seriously threatened the normal production and life and social and economic development of urban people.The frequent occurrence of urban flooding is the result of a combination of factors.Climate change,accelerated urbanization,and backward regional drainage systems have exacerbated urban flooding disasters.How to accurately simulate the process of urban runoff from rainfall to surface water reclamation,quantify urban flooding disasters,and predict urban flooding has become an urgent problem for urban development.For coastal cities,when heavy rainfall occurs for a short period of time,the overloaded rainwater cannot be discharged into the urban drainage system in time,forming surface water accumulation and inducing urban flooding disasters.In the event of high tide,the high tide level has a jacking effect on the urban drainage system.Urban drainage Unsatisfactory,a large amount of rainwater accumulated on the surface formed a serious urban flooding disaster.Taking Nantai Island of Fuzhou as a research area,the Info Works ICM urban comprehensive drainage model was used to construct a coupled hydrological and hydrodynamic model of storm urban flooding in Nantai Island,and the coupled urban flooding model after inspection was used to analyze the overflow and surface of Nantai Island pipe network under different scenarios of rainfall.Urban flooding was simulated to analyze the urban drainage system load and urban flooding disasters.Based on the urban flooding coupling model,the model water level boundary was adjusted,and combined with deep learning LSTM(Long Short-Term Memory)Nantai Island urban flooding to simulate the prediction.The main contents are as follows:(1)Research on the urban flooding coupling model of Nantai Island.Use Info Works ICM to construct urban hydrological model,1D river network hydrodynamic model,1D pipe network hydrodynamic model and 2D surface flooding model,and couple them.The water level boundary of the urban flooding coupling model is the river level in Nantai Island.Use the data such as the water depth and accumulated water range of the land area under the rain of "Sudiruo" to determine the parameters of the urban flooding coupling model;use the data such as the water depth and accumulated water range of the water area under the rain of the "Catfish" typhoon to verify the coupling of urban flooding model.Under two typhoon rainfalls,the average error between the simulated water depth and the measured water depth is 4.42%and 12.70%,respectively.The simulated water accumulation range is consistent with the measured water accumulation range,indicating that the verified urban flooding coupling model is suitable for Nantai Island drainage System analysis and urban flooding disaster identification.(2)Simulation study on urban flooding in rainfall scenarios on Nantai Island.Based on the rainstorm intensity formula in Fuzhou City,seven kinds of rainfall scenarios with different recurrence periods were designed.Using the urban flooding coupling model,the flooding and surface water accumulation of the Nantai Island pipeline network under each rainfall scenario were simulated and analyzed.The simulation results show that in the following three-year and three-year rainfall scenarios,the water accumulation area of the whole area is less than 3.62km2,the maximum water depth is less than 2.03m,and the area with water accumulation exceeding 24h is less than 0.45km2.The overall drainage capacity of Nantai Island is good The urban drainage system can undertake most of the surface runoff;once in a five-year rainfall scenario,the water area of the whole area is 4.95km2,the maximum water depth is 3.30m,and the area where the water exceeds 24h is 0.94km2.The Nantai Island drainage system is nearly saturated.The local area exceeds the upper limit standard;in the case of more than 10 years and 10 years of rainfall,the area of accumulated water exceeds 8.82km2,the maximum depth of accumulated water exceeds 4.01m,and the area of accumulated water exceeds 24h exceeds 3.56km2.The additional rainwater cannot enter the drainage In the system,all the accumulated surface and local urban flooding disasters in some areas continue to increase as the rain intensity continues to increase.Analysis of the flood-affected areas shows that the overall level of pipe network laying in the eastern region of Nantai Island,which has a higher urbanization level,is higher than that in the central and western regions.The inspection wells with large overflows during rainstorms are mainly distributed in the central and western regions."Dongqing" distribution;urban flooding disasters in Nantai Island are jointly affected by many factors such as urban natural topography,intensified surface changes,surface runoff,and low capacity of urban drainage systems.(3)Prediction study of urban flooding on Nantai Island.First,based on the urban flooding coupling model,add sluices,pumping stations along the river and their operating rules to connect the Minjiang River and the inland river,and construct a urban flooding prediction model for Nantai Island.The waterfront boundary of the urban flooding prediction model is the tidal level of the Minjiang River;then,on January 1,2019 From day to May 17,the Minjiang tide level data is used as a sample,and LSTM is selected to construct a recurrent neural network.The network is trained,verified and tested under the foreseeable period of hourly,half-day and day-by-day,and the tested network is used to predict the Minjiang tide level;Finally,on May 18th,the Bureau of Meteorology pushed rain and predicted the tidal level of the Minjiang River to simulate and predict the overflow and surface water accumulation of the Nantai Island pipeline network.The loss of the verification set under each predictive period of the cyclic neural network is 0.1410,0.3786,and 0.7006 respectively.The hourly prediction method with the smallest loss of the verification set is selected to predict the tidal level of the Minjiang River in a circular manner.The results of the flood prediction on May 18 show that the surface of Nantai Island The overflow is concentrated in the southeast and northeast,the surface water accumulation area reaches the maximum at 19:55,which is 2.52km2,the maximum water depth is 1.76m,and the area of water accumulation over 24h is 0.64km2.Match.The combination of LSTM and flood forecasting model on Nantai Island has solved the problem of flood forecasting on Nantai Island.This article provides theoretical basis and technical support for the prediction and prevention of urban flooding in Nantai Island of Fuzhou City,and can also provide reference and reference for the prevention and control of urban flooding in other cities.