A Study On Risk Variation Of Flood Disaster In Area Along Yangtze River In Anhui Province

Flood disaster is one of the most serious natural disasters in current world, and it brings great casualties and economic loss.China is one of the countries which have the most serious flood disaster. Flood risk research is the precondition and foundation to scientifically and effectively undertake flood protection and disaster reduction. This essay took areas along Yangtze river in Anhui province as study area. Data source contained precipitation data, remote sensing images, foundamental geographic information and socioeconomic statistics. Through application of relevant mathematical methods and geographic technique, we assessed flood risk of study area in 1990, 2000 and 2007. Then we obtained corresponding flood risk rank and index. Finally, we analysed flood risk rank variation, index variation and landscape pattern variation.the conclusion included following aspects:Assessment of flood risk. Firstly, on basis of precipitation data, remote sensing images, foundamental geographic information and socioeconomic statistics, we selected ten indexes, such as mean annual precipitation amount, vegetation coverage rate, elevation standard and population density. Secondly, we applied analytical hierarchy process and entropy-weighted technique to obtain weights of corresponding indexes. Thirdly, we assessed flood risk of study risk of study area supported by fuzzy comprehensive evaluation method and GIS technique. On spatial distribution pattern, flood risk rank and index had the same tendency that they increased from south to north. High risk mainly concentrated on northern region and both sides along main stream of Yangtze river. Low risk mainly concentrated on southern mountain areas and some areas of western region. On constitution of risk ranks, the sum area of the highest risk zone and the higher risk zone was 18648.28km2,accounted for 1/3 of the total area.The proportion of moderate risk zone,lower risk zone and lowest risk zone were 23.12%, 20.01% and 18.89%.On constitution of risk ranks in each county, Maanshan, Lujiang, Tongling City and Chaohu etc had higher risk;and on mean risk index in each county, the highest index of the top three was Lujiang,Chaohu and Maanshan,and the value were 3.732,3.511 and 3.382.The government should enhance flood warning and protection in these places.Risk variation analysis of flood disaster.According to the results of risk assessment in 1990,2000 and 2007,risk variation was analyzed in the study area 1990~2000, 2000~2007 and 2000~2007 stages,including risk rank variation,risk index variation and risk landscape pattern variation.In the aspect of risk rank variation,spatial distribution of risk rank was changed.The proportion of highest risk zone first increased and then decreased,the proportion of highest risk zone decreased from 39.33% in 1990 to 29.18% in 2007,and decreased in the whole period,and differences in the area decreased.The variation velocity was high in every risk rank zone in different period,but low in the whole period.The variation velocity differed in different period in every risk rank.In the aspect of risk index variation,the degree and distribution range of risk index variation differed in different period.The variation amplitude of flood risk index was small in the whole study period,was -1.655~1.412,and there was no increasing intensely area and decreasing intensely area.In the level of county,the defference of average variation of flood risk index was not obvious in the whole study period,and its value was between -0.2 and 0.45.In the aspect of risk landscape pattern variation,the fragmentation of risk landscape was decreased and the diversity was increased,and the structure of the inlaid high-low risk was showed.The variation trend of landscape pattern in every risk zone was intensely different,but the highest risk zone and the higher risk zone showed concentration distribution,and it illustrated the possibility that the regional flood risk may be higher.