Research On Risk Assessment Of Flood Disaster In Zhengzhou Based On RS And GIS

Flood disaster is a serious natural disaster.Zhengzhou,as the capital of Henan Province,occupies an important position in the development of national strategy,while the risk of flood and waterlogging restricts the local development and threatens the property safety of the people.Zhengzhou city is facing a great historical opportunity.At the same time,it has important social and economic benefits to carry out flood disaster risk assessment and master the spatial distribution and risk level division of flood disaster risk in Zhengzhou city.In this paper,Zhengzhou city is taken as the research area,and remote sensing data is taken as an important data source.At the same time,combined with the grid geographical background data and the spatial socio-economic data,using GIS technology,the data are processed and analyzed in space,and the risk assessment of flood disaster in Zhengzhou is studied.The main research results are as follows:(1)Based on the MODIS data of long time series,the hazard of flood disaster in Zhengzhou city is evaluated preliminarily.Download MODIS data from June to August of 2009-2018 on NASA website.According to the band characteristics of image data,the band operation is carried out in Arc GIS software to determine the threshold value of water body,extract the information of water body in flood season,wipe off the normal water body in flood season,and obtain the submergence range of water body in flood season at the corresponding time point.In order to get the data of inundation frequency of flood water in Zhengzhou City,the 10-year flood water body was analyzed in Arc GIS software.It can be seen from the result chart that the areas with high inundation frequency of flood water body in Zhengzhou are mainly concentrated near the Yellow River main stream in the northwest direction and the urban area of Zhengzhou,and the inundation frequency of other areas is relatively low.(2)According to the formation mechanism of flood disaster,from the three aspects of flood hazard,vulnerability and weakness of disaster prevention and mitigation,according to the four principles of comprehensiveness,operability,adaptation to local conditions and sensitivity,12 index data are selected to construct the flood disaster risk assessment index system of Zhengzhou.The data are processed in the Arc GIS software in a unified spatial way,and the weights of each index are determined by the analytic hierarchy process.Then,the risk assessment grades of flood disaster in each area of Zhengzhou City are obtained by the fuzzy comprehensive evaluation method,and the results of risk assessment are expressed in two scales of grid unit and administrative unit.It can be seen from the results that the areas with higher risk level are mainly concentrated in the urban center of Zhengzhou,followed by the southwest part of Zhengzhou,and the risk level of other places is lower.(3)The fuzzy three-dimensional coordinate method based on the fuzzy mathematics theory is put forward and verified in Zhengzhou city.In this method,the three-dimensional space coordinate system is involved in the process of fuzzycomprehensive evaluation.The three coordinate axes of the three-dimensional space coordinate system are hazard,vulnerability and vulnerability of disaster prevention and mitigation,and the index weight is the unit scale value.Each area is drawn into coordinate points and displayed in the fuzzy three-dimensional space coordinate system,and the distance from the coordinate point to the origin indicates the risk.For this method,the concepts of risk grade surface,risk grade curve and risk grade point are proposed.In the three-dimensional visual expression of the results,the risk grade and risk characteristics of flood disaster in each area of Zhengzhou city can be displayed,and the subordinate degree of adjacent risk grade in each area can also be displayed intuitively.Dimension reduction can be realized by using the attributes of3 D coordinate system,and the number of first level indexes can be reduced in the result of risk assessment.At the same time,the results of fuzzy comprehensive evaluation method and fuzzy three-dimensional coordinate method are compared.From the comparison of the results of the two methods,it can be seen that there is little difference in the assessment results.The risk assessment results of the Zhongyuan District,Jinshui District and Erqi District are the same,all of which are of high risk.The assessment results of Huiji District and Guanchenghuizu District are slightly different.In the fuzzy comprehensive evaluation results,the risk level of Huiji District is low risk,the risk level of Guanchenghuizu District is medium risk,while in the fuzzy three-dimensional coordinate evaluation results,the risk level of Huiji District is medium risk,and the risk level of Guanchenghuizu District is low risk.