Var iation Tr ends and Multi- scale Analysis of Flood Affected Area in Var ious Regions of Xinjiang
新疆不同区域洪灾受灾面积变化趋势及多尺度分析

In this paper,we selected and used 2038 flood disaster data from 84 counties of Xinjiang in 1950-2006,and adopted the gray relational evaluation model,taking county as a unit,to divide Xinjiang into heavy flood disaster subregion,secondary heavy flood disaster subregion,general flood disaster subregion,light disaster flood subregion and tiny flood subregion.We also adopted autoregression moving average model ARMA(p,q) and second order principal value function to analyze long-term trend of disaster affected area,as well as its oscillation cycle with Morlet wavelet.Results show that the flood affected area throughout the region and every subregion had a changing cycle of 12-15a,the flood frequent oscillation cycle was on interdecadal and interannual scale of climatic background after the 1980s,and the superposition of small oscillation cycle as 7-8a and 2-3a was comparatively frequent.In terms of the flood disaster variation trend of Xinjiang,the outlook is not optimistic for the general flood affected area presented a distinct increasing trend and each flood subregion was in the climatic background with frequent period of flood at present.The distributing trend of flood disaster affected area and the oscillation cycle in the north and south piedmonts of the Tianshan Mountains played a decisive role relating to the interannual long-term trend and its oscillation cycle in the flood affected area in Xinjiang.These regions were the keys in reinforcing facilities and strength for flood prevention and control.Otherwise,the general flood affected area would have a greater impact on the flooded area of entire Xinjiang,leading to an increasing trend in the future regardless of the short,medium or long period changes,hence great attention should be aroused.