Simulation Of Rainfall And Evaluation Of The Optimization Effect Of Measures In Urban Area Of Handan City

In recent years,global warming and the rapid increase in urbanization have led to changes in urban rainfall and runoff processes,resulting in an increase in flood peak flow.Due to the increase in impermeable areas within the city and the inadequate design of existing pipelines to meet practical needs,Rainwater cannot be discharged in a timely manner,resulting in the formation of stagnant water on the surface,resulting in urban waterlogging.Urban waterlogging has become one of the important factors restricting the country’s economic and social development.Therefore,it is necessary to use urban rainwater flood models to analyze and assess the risk of urban waterlogging in areas prone to waterlogging.This study applied the MIKE URBAN model,MIKE 11 model and MIKE 21 model to establish a one-dimensional and two-dimensional hydrodynamic coupled urban rain flood model in Handan City,Hebei Province.Then,analyzed the waterlogging situation in the study area under different return periods from the overflow nodes of the pipeline network,pipeline load,surface water depth,and water accumulation area.Designed and analyzed different scheduling schemes for the drainage pump stations on the river channel in the study area,and evaluated the effectiveness of different measures.The following results were achieved:(1)The urban storm flood model in the study area were constructed,and used measured rainfall data and waterlogging data to calibrate and verify the model parameters.Design rainfall with a return period of 1a,3a,5a,10 a,and 20 a and a duration of 2 hours was designed.Then,analyzed the waterlogging risk for the entire study area from the aspects of overflow nodes of inspection wells,surface ponding depth,and ponding area.The results showed that the peak intensity of rainfall and total rainfall increased with the increase of the return period,and the number of overflow nodes,maximum surface water accumulation depth,water accumulation area,and waterlogging area of the collection well also increased.This indicated that rainfall affects the maximum water accumulation depth on the ground,in turn affected the total area of waterlogging in the entire region,and the increase in waterlogging area leads to an increase in the risk of regional waterlogging.Through the analysis of regional waterlogging risks,it was found that the waterlogging depth at the intersection of Yuxin Street and Congtai Road,as well as the intersection of Greening Street and Heping Road,is greater and the waterlogging risk is higher.Compared to other waterlogging points,the waterlogging depth at the intersection of Guangming Road and Zhanzhan Road,as well as the intersection of Fuhe Street and Congtai Road,is smaller.However,there are also certain waterlogging risks,and regional waterlogging warning and drainage work should be strengthened.(2)Designed and simulated different scheduling schemes between the existing 4pumping stations,and select the optimal scheduling scheme: When the water level in front of the station reaches 54.65 m of the lowest control level,start the # 1 pump station;When the water level in front of the station reaches 55.2m,start the # 2 pump station;When the water level in front of the station exceeds 55.95 m,# 3 and # 4 will be turned on,that is,all will be turned on.Closing method: When the water level in front of the station is lower than 55.95 m,# 3 and # 4 are closed,leaving # 1 and # 2;When the water level in front of the station is lower than 55.2m,# 2 is closed;When the water level in front of the station is lower than 54.65 m,# 1 will also be closed,that is,all pump stations will be shut down.(3)Under the same rainfall scenario,compared the runoff coefficients of optimized pumping station scheduling schemes and different LID single measures,and analyzed the reduction and control effects of different schemes and measures on regional runoff.Comparative analysis found that the reduction rate of permeable pavement is between19% and 52%,with the best effect;the optimal scheduling scheme for pumping stations is better,12.99%;and the rain bucket is the weakest,between 2% and 8%.The above research results provide technical tools for urban rainwater and flood management in Handan City,support the optimization of urban waterlogging management measures,and provide reference for waterlogging prevention and control management in other cities in North China.