Simulation Of Waterlogging In Xiushan County Of Chongqing City Based On Mike Software

With the rapid development of China’s economy and the accelerating process of urbanization,coupled with global climate change and frequent extreme rainfall events,urban waterlogging in China is frequent,posing a great threat to the safety of people’s lives and property.Urban waterlogging caused by extreme rainfall is,on the one hand,due to the rapid development of urbanization,the urban surface hardening area continues to increase,thus increasing the surface impermeability,and thus increasing the runoff.On the other hand,the design standards of some urban drainage pipe networks fail to meet the requirements of relevant codes,and the drainage capacity of the pipe network is insufficient when it encounters extreme rainfall for a certain number of years.Therefore,the application of mathematical model to evaluate the current drainage capacity of a city and to predict the areas where waterlogging may occur can provide a scientific basis for reducing the risk of waterlogging in a city.Taking the sponge city built-up area of Xiushan County,Chongqing City as the research area,this study combined the Mike Flood coupled Mike Urban one-dimensional pipe network model and Mike 21 two-dimensional surface overflow model to simulate the Urban waterlogging situation under different rainfall intensities,and put forward relevant suggestions.The main contents are as follows:(1)Based on the collected basic data,the Mike Urban one-dimensional pipe flow model and the Mike 21 two-dimensional surface model were successfully constructed.Coupled successfully through Mike Flood manhole connection.The accuracy of the coupling model is verified by measuring the rainfall and monitoring the water level changes of the rainwater nodes,calibrating and verifying the hydrological and hydrodynamic parameters of the model,and by measuring the water depth and location of the rainwater points on the same day.(2)the short-term duration of 3h and the recurrence periods of 1a,2a,3a and 5a were taken as the rainfall boundary conditions.The overflow value of the rainwater pipe and the overflow value of the rainwater node as the evaluation criteria.The length of pipes with drainage capacity between 1A and 5A is 7.28 km,and that larger than 5A is47.54 km,accounting for 10.34%,11.91% and 77.76% of the main pipe length,respectively.The number of overflow nodes in 1A,2A,3A and 5A was 37,61,72 and84,accounting for 6.29%,10.37%,12.24% and 14.29% of the total,respectively.The drainage effect of Shangxiushan County is good on the whole,but in terms of details,the designed return period of drainage capacity of rainwater pipes of the city’s main trunk road is less than 1A,and waterlogging is easy to form in low-lying areas.(3)Taking short duration of 3 hours,return period of 20 a,30a and 50 a as rainfall boundary conditions,ponding depth and ponding time as evaluation indexes,the waterlogging risk regions are divided into three grades: waterlogging risk free region,waterlogging light risk region,waterlogging low risk region,waterlogging medium risk region and waterlogging high risk region.The scenario simulation evaluation method based on Mike flood coupling model is used to evaluate the waterlogging risk in the study area.By comparing the regional distribution of waterlogging risk in three return periods,three waterlogging prone areas are identified,which are T-junction at the junction of Yuxiu Avenue and Fengxiang road;Lingyuan road;About 200 m from the junction of Fengxiang road and Shilian road to Shilian road.In other regions,the increase of low-risk waterlogging area is the largest,and the increase of middle risk waterlogging area is the smallest.The causes of high-risk waterlogging areas are analyzed.The three waterlogging prone areas are affected by many factors,such as low-lying terrain,more surrounding buildings,rainwater pipe network and so on.(4)In order to effectively prevent and control urban waterlogging,engineering measures and non engineering measures are taken.In the engineering measures,it is proposed to improve the design standard of rainwater pipeline and add "green" measures to reduce the impervious rate of waterlogging prone areas,and two waterlogging prevention schemes are put forward.Scheme 1 is to add "green" measures,and scheme 2 is to add "gray" measures on the basis of scheme 1.Two waterlogging prevention schemes are simulated with a short duration of 3 hours and a return period of30 years as the boundary conditions,The simulation results of scheme 2 are significantly better than that of scheme 1,and the reduction rate of waterlogging risk area is the highest.In the non engineering measures,it puts forward suggestions to improve the daily management and emergency management.