| In recent decades,with the changing global climate,increasing urbanization and the growth of impervious areas in cities,urban flooding caused by extreme precipitation has gradually increased,resulting in more severe disasters.Zhengzhou is the political and economic center of Henan Province and has a huge responsibility for economic development,its high level of social development concentrates a large number of people,which can have very serious consequences in case of flooding.For example,in the "7-20" disaster in Zhengzhou in 2021,the Zhengzhou Subway line 5 suffered a serious disaster.The paper takes the above disaster as a starting point to evaluates the comprehensive risk of subway flood in Zhengzhou from the disaster system theory and classify the corresponding levels,which could not only enrich the comprehensive risk theory of Zhengzhou Subway flood disaster,but also provide scientific basis for flood control and disaster prevention and urban public safety management.The paper determines the weights or coefficients of 17 indicators at its impact level by means of hierarchical analysis,entropy weighting and logistic regression,and establishes a comprehensive risk assessment model for Zhengzhou Subway flood from four levels: hazard,exposure,vulnerability and flood mitigation capacity to get the results of the assessment of Zhengzhou Subway stations.The main conclusions are as follows:(1)M-K mutation test and wavelet analysis were used to analyze the precipitation situation and regularity in Zhengzhou.The average precipitation of Zhengzhou in July and August accounted for 44.7% of the total annual precipitation.Rainfall mainly occurred in July and August,accounting for 61.2% of the annual frequency.The annual precipitation of Zhengzhou city showed a sudden increase in several time nodes,showing a slow increasing trend as a whole;there was no abrupt increase in annual rainy days.Here are several quasi-cycles of annual precipitation series in Zhengzhou,which were 3 years,8 years,14 years and30 years,among which the 14-year cycle is the most significant.There were five quasi-cycles in the annual rainfall days series,which were 3 years,8 years,14 years,20 years and 51 years,among which the 14-year cycle is the most significant in the whole study period.(2)Based on the four aspects of risk,exposure,vulnerability and flood control and disaster prevention capability of disaster risk theory,Zhengzhou Subway flood disaster was respectively evaluated.There were117 subway stations in the main urban area of Zhengzhou.In the risk assessment,12 stations,such as Erqi Guangchang Station and Zhengzhou Railway Station,were in high risk,accounting for 10.3%,26.5% of the stations were in medium-high risk or above,31.26% of the stations in Line 5 were in medium-high risk or above.In the exposure assessment,7 stations,including Erqi Guangchang Station and Henan People’s Hospital Station,were in the high exposure level,accounting for 6%,24.4% of the stations were in the medium-high exposure level or above,42.86% of the stations in Line 3 were in the high exposure level or above.In the vulnerability assessment,the vulnerability results were divided into four different periods according to the passenger flow of the subway stations.(1)In the morning of working days,7 stations,including Huanghe Road Station and Xisanhuan Station,were in high vulnerability,accounting for 6%;the stations of medium high vulnerability or above accounted for 27.35%;53.13% of the stations of Line 5 were in medium high vulnerability or above.(2)In the afternoon of working days,11 stations,including Henan University of Technology Station and Erqi Guangchang Station,were in high vulnerability,accounting for9.4%,the stations of medium high vulnerability or above accounted for 34.19%,and 62.51% of the stations of Line 5 were in medium high vulnerability or above.(3)In the non-working mornings,7 stations,including Henan University of Technology Station and Xisanhuan Station,were in the high vulnerability level,accounting for 6%,23.07% of the stations were in the medium-high vulnerability level or above,and 40.63%of the stations on Line 5 were in the high vulnerability level or above.(4)In non-working afternoons,10 stations,including Henan University of Technology Station and Zhengzhou University Sci-Tech Park Station,were in high vulnerability,accounting for 8.5%,30.77% of the stations were in medium-high vulnerability or above,and 65.63% of the stations in Line 5 were in high vulnerability or above.Taking a comprehensive view of the situation of differentperiods,12 stations,including Wuyi Gongyuan Station and Qinling Road Station,were in high vulnerability,accounting for 10.3%,36.76% were in medium-high vulnerability or above,65.63% of the stations in Line 5 were in medium-high vulnerability or above.In the evaluation of flood control and disaster prevention capacity,12 stations including Zhengzhou Railway Station and Erqi Guangchang Station had higher flood control and disaster prevention capacity,accounting for 10.3%,stations with medium-high flood control and disaster prevention capacity accounted for 26.5%,61.9% stations of Line 3 were in medium-high or above flood control and disaster prevention capacity.The above were evaluations of the four aspects of flood disaster of Zhengzhou Subway.From these four aspects,different preventive measures can be taken for Zhengzhou Subway stations according to the actual situation,so as to improve the disaster prevention ability of Zhengzhou Subway stations in the event of flood disaster.(3)Comprehensive risk assessment of flood disaster in Zhengzhou Subway.According to different vulnerability conditions,the comprehensive risk assessment results were divided into four types:(1)In the morning of working days,12 stations such as Erqi Guangchang Station and Xidajie Station were at high risk,accounting for 10.3%;the number of stations at medium high risk or above accounted for 24.79%;33.33%of stations on Line 1 were at medium high risk or above.(2)In the afternoon of working days,11 stations such as Erqi Guangchang Station and Zhengzhou Railway Station were at high risk,accounting for 9.4%.The number of stations with medium-high risk or above accounted for 28.21%.37.5% stations of Line 5 were at medium-high risk or above.(3)In the morning of non-working days,12 stations including Renmin Road Station and Erqi Guangchang Station were at high risk,accounting for 10.3%;the number of stations with medium-high risk or above level accounted for 26.5%;34.38% of Line 5 stations were at medium-high risk or above;(4)In the afternoon of non-working days,5 stations including Zhengzhou Railway Station and Dongfeng Road Station were at high risk,accounting for 4.3%.The number of stations with medium-high or above comprehensive risk accounted for 23.93%.37.5% of stations on Line 5 were at medium-high or above comprehensive risk.Considering the situation of different time periods comprehensively,9 stations,including Erqi Guangchang Station and Zhengzhou Railway Station,were at high risk,accounting for 7.7%,the number of stations with medium-high risk or above accounted for 27.4%,and 37.5% stations of Line 5 were at medium high risk or above. |
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