Research On Flood Risk Assessment In Jiangxi Province Based On GIS And RS

Floods,as one of the most recurrent,extensive and common natural disasters in the world,seriously threaten the socio-economic development of the region and the production and life of the people.As an important non-engineering preventive measure against floods,flood risk assessment can provide scientific reference for the formulation of regional disaster prevention and mitigation policies and disaster preparedness and management work.Jiangxi Province is located on the south bank of the middle and lower reaches of the Yangtze River,with well-developed river systems and abundant rainfall,and is one of the most frequent flooding provinces in China,so it is very important to strengthen the research on flood risk assessment.This paper takes Jiangxi Province as the research area,based on long time series remote sensing image data,gridded physical geographic data and spatial socio-economic data,and uses GIS technology to extract information and spatial analysis of each data,and carries out research on flood risk assessment in Jiangxi Province with the help of hierarchical analysis method,entropy power method and fuzzy synthesis assessment method.The main work and results of the dissertation research are:(1)Preliminary assessment of flood risk in Jiangxi Province using Landsat8 data of long time series.Historical flood water body inundation frequency information is an important reference for flood risk assessment.In this paper,we used Landsat8 data during 2013-2021 for the spectral band characteristics of this image data,combined with the water body index method in ENVI5.3 software for band operation and wave spectrum analysis to determine the threshold value of flood water bodies,and extracted the flood water body area in Jiangxi Province during 9 years.Comparing the normal water bodies in 2021,the frequency of inundation of historical flooded water bodies in Jiangxi Province was analyzed by using the overlay analysis function of Arc GIS software,and the preliminary assessment results of flooding hazard in Jiangxi Province were obtained.The preliminary assessment results show that the high risk and sub-high risk areas of historical flooding water bodies in Jiangxi Province are mainly concentrated in the north near the main streams of Poyang Lake and its converging water system,and the low risk and sub-low risk areas are mainly concentrated on both sides of the tributaries of major rivers in the province.(2)According to the natural disaster risk system theory,the formation mechanism of flood disaster is explored,and the primary indexes for flood disaster risk assessment in the study area are established from the four risk elements of flood hazard,sensitivity,vulnerability and disaster prevention and mitigation capacity.In addition,combining the principles of scientificity,comprehensiveness,purposefulness,operability and localization,the average annual number of heavy rainfall days,average annual rainfall,flood inundation frequency,relative elevation,absolute elevation,soil erodibility,vegetation cover,river network density,population density,per capita GDP,land use type,gross regional product,per capita disposable income,number of beds per 10,000 and other 14 secondary indicators to construct a flood risk assessment index system in the study area.Using Arc GIS software to geographically process and spatially analyze the 14 index data,we obtained 14 1km×1km gridded raster data index distribution maps for flood disaster risk assessment in Jiangxi Province,based on which,we combined and assigned weights to each index by hierarchical analysis method and entropy weight method,and used fuzzy comprehensive evaluation method to determine the affiliation function and fuzzy relationship matrix,and finally obtained the study area The results of flood risk assessment and risk zoning map were obtained.(3)The risk assessment results of flood disasters in Jiangxi Province were expressed based on two scales: raster cells and administrative cells.The risk assessment results show that the high-risk flood areas in Jiangxi Province are mainly located in the Poyang Lake Plain in northern Ganxi,the transition zone of the hilly plains in eastern Ganxi and the river valley basin area in northeastern Jiangxi,while the western,northwestern and southern Jiangxi Province are generally low-risk flood areas except for a few scattered areas with high risk.From the county scale,Xunyang District,Gongqingcheng City,Qingshan Lake District,Donghu District,Xihu District,Nanchang County,Zhushan District,Yujiang County,Yuehu District and Xinzhou District are high risk counties(cities)for flooding;22 counties and cities such as Chaisang District,Hukou County,Lushan City,Duchang County and Poyang County are secondary high risk counties(cities),and the rest of the counties and cities are medium risk and below areas.The paper is mainly based on remote sensing image data,meteorological observation data,geographic information data and society and economical data,etc.Combined with the theory of disaster risk system,the index system of flood disaster risk assessment in Jiangxi Province is constructed.The spatial expression of various data is realized by using the geographic processing and spatial analysis function of GIS,and the flood disaster in Jiangxi Province is evaluated with the help of combined weight results and fuzzy comprehensive evaluation method,and the evaluation results can provide reference and support for flood disaster risk management and flood relief work in Jiangxi Province.