Safety Assessment And Flood Hazard Analysis Of Huangpu River Flood Wall In Shanghai

Shanghai is the most important city on the east coast of China.Affected by climate change and its own urban development,the eastern metropolis is under threat from floods.The huangpu river runs through downtown Shanghai,making it one of the city’s main flood sources.In typhoon season,fierce typhoons bring heavy rainfall and wind and water.If they meet with the astronomical high tide,they will bring huge pressure to the flood control of the entire huangpu river.For decades,in order to ensure the safety of people’s lives and property,the flood control system along the huangpu river has been continuously strengthened and strengthened,and governments at all levels have also invested enormous manpower and material resources.Of this study is to draw lessons from the Dutch VNK2 levee system of flood risk analysis method of flood prevention wall of huangpu river in Shanghai as a case study area,based on Shanghai’s high resolution terrain elevation data,a comprehensive collection of the huangpu river left and the right bank dike design data,geological exploration data,history and be or get out of danger,determine the pattern of huangpu river flood wall crash,the Prob-2b probabilistic calculation model of nested MC method and FORM method for embankment flood dike,bursts of probability calculation,evaluate the safety of flood prevention wall of huangpu river;On this basis,considering the climatic and non-climatic factors such as sea level rise and land subsidence,the flood risk analysis of the failure section of flood prevention wall of huangpu river is carried out,and the following conclusions are drawn:(1)By considering climate and non climate factors such as future sea level rise and regional land subsidence,this study predicts the future appreciation of Shanghai relative sea level.Taking 2010 as the base year,the predicted values of 5%-95%confidence interval in 2030,2050 and 2100 are 11-32cm(best predicted value:21cm),25-65cm(best predicted value:45cm)and 56-148cm(best predicted value:136cm)respectively in RCP2.6 scenario,and 12-32cm(best predicted value:22cm)and27-73cm(best predicted value:27-73cm)respectively in RCP8.5 scenario value:50cm),75-197cm(best prediction value:136cm).(2)In the calculation of levee failure,the main factors affecting the levee failure are the water level and the elevation behind the flood control wall.According to the calculation results,the levee failure section with the probability of levee failure greater than 50%is extracted.Under the scenario of RCP8.5,when the flood level occurred once in 1,000 years,the length of the burst section reached 53.8 km,accounting for 16.8%of the total length of the flood prevention wall of the huangpu river.From the perspective of the spatial distribution of the levee bursting section,the levee bursting section shows the characteristics of more upstream and downstream ends and less middle reaches.Moreover,the levee bursting section starts from the upstream Qingpu district near qingxi country park.The length of the levee bursting is600m and the probability of the levee bursting is 78%.The most severe cases,in 2100,the flood prevention wall of huangpu river in the highest water level of 7.95 m,probability of levee breaches from 54%to 100%,spatial distribution,the upstream in the Qingpu district Mao almost across the river levee breaches,downstream,baoshan district,hongkou district north bund,Shanghai huangpu district shiliupu pier spreading magnificent river container port military road,Yangpu district,Shanghai fishing vessels factory,Pudong district,Shanghai xinhua harbor company will happen serious levee breaches.(3)In the calculation of overflow dike,the main factors affecting overflow dike are the elevation and storm height of flood control wall.It is concluded that the probability of overflow dike is 1 when the water level is higher than the measured elevation of flood control wall.According to the calculation results,the flood wall overflow section of the huangpu river and its proportion in the total length of the flood wall are obtained.The results show that,under different scenarios,with the increase of the recurrence period and the increase of the flood level,the more dike overflow events occur.Under the scenario of RCP8.5,99.5%of the flood wall will overflow the dike.In terms of spatial distribution,under the most severe scenario,it will affect the flood control wall along the whole huangpu river basin,involving 9administrative regions such as Qingpu district,Songjiang district,Minhang district and Baoshan district in the upper,middle and lower reaches.(4)Over time,the process of the flooding of the river shows three main pattern.First of all,each different years return period showed the submerged depth of change over time rapid increase at first and then fell back quickly,finally submerged depth gradually warming trend,the largest submerged depth in the river Banks,dyke break after an hour;Secondly,with the advance of time,the amount of water that overflows from the flooded section and the flooded section of the flood control wall keeps increasing,and the change of the flooded area shows a trend of rapid increase first,and then the increase of the flooded area gradually slows down.The time inflection point roughly appears in the fifth hour or so of the flood evolution.The possible reasons are as follows:the terrain on both sides of the huangpu river is relatively flat and open,and the flood discharge function of the river is stronger,leading to the rapid increase of the flooded area over time;After the 5th hour,the submerged area increased slowly,which was mainly due to the continuous accumulation of river flood in low-lying areas and the difficulty of overflow due to the terrain restrictions.Finally,the inundation process in RCP8.5 is similar to that in RCP2.6,but due to the extreme high flood level,the inundation is more serious in RCP8.5,and the maximum submergence depth is larger.The flood discharge capacity of the river brought by the high water level is greatly enhanced,resulting in the continuous rise of the flooded area.(5)In different years,with the increase of the return period,the submerged area and submergence depth of river flood in each administrative region of Shanghai also increased.Taking the once-in-1,000 years scenario as an example,the flood of huangpu river in each year was distributed along the river course in a strip,and the submergence depth decreased with the distance from the river course.River flood in the process of travel,with the terrain ups and downs to the inland spread,in the low-lying areas easy to form water,causing flooding.In 2010,the maximum submerged land area of Shanghai was 262.3km~2,accounting for 5.02%of the total land area of Shanghai.The upstream area was the most seriously submerged,with the maximum submerged depth of 7.72 m.RCP8.5 scenario,2030,2050,2100,the largest water area of 616.21 km~2,992.83 km~2,2430.77 km~2,11.81%of the land area of Shanghai,respectively,19.03%,46.60%,in addition to the Jiading district,the affected area of the smallest,the rest of the district have been flooded land,such as the bund,north bund,Lujiazui business district,Shanghai jiaotong university,east China normal university,zizhu national high and new science and technology park,and other institutions of higher learning,scientific research institutes,upstream qingpu,songjiang,such as agricultural land,As well as road traffic,residential and so on were seriously affected.This article is only preliminary exploration of the huangpu river flood wall safety evaluation methods,in bursts,overflow on the choice of evaluation method and parameter Settings affected by lack of relevant data,the result has a certain influence,the future study of huangpu river flood wall under the flooding can be further expanded in the following aspects:first,through a large number of field survey,to obtain more accurate physical parameters,to further improve the identification method of flood prevention wall failure risk.Secondly,based on the distribution of flood risk in the case of failure of flood wall in huangpu river,the emergency response and emergency management of critical infrastructure can be studied.