Flood Encounter Analysis Of The Upper Yangtze River Based On Set Pair Analysis Theory

Flood encounter concerns the overall flood control safety of river basins,and makes the river flood control situation more severe.The Yangtze River has a vast basin area,numerous tributaries,frequent flood disasters,while developed economy along its coast.Especially in the upstream,the flood encounter situation of the main stream and tributary,tributary and tributary is different.In order to reduce the loss caused by the flood disaster,it is necessary to analyze the flood encounter situation in the Yangtze River basin comprehensively and systematically,and evaluate the flood encounter schemes under different inflow conditions reasonably.In this paper,the flood encounter problems in the main stream and tributary of the upper Yangtze River are systematically analyzed and studied,including the set pair situation ordering of flood encounter and the assessment of flood encounter schemes.In terms of set pair situation ordering of flood encounter,first based on the basic concept of set pair situation ordering and the set pair situation ordering method of four-element connection number,by comparing with the relationship of size between identical degree,diversity degree and opposite degree,a set pair situation ordering method of five-element connection number is proposed.Then the statistical law of ten flood encounter combinations in the upper Yangtze River basin is analyzed,and the flood encounter situations of ten different combinations in the main stream and tributary are ordered by set pair situation.It is concluded that the maximum overlap of flood process for 7 days and 15 days in the upper Yangtze River is in a serious state,and the encounter and superimposing of flood process for a long time brings great flood control pressure to the lower reaches,which should be paid enough attention.In terms of the assessment of flood encounter schemes,first a grade evaluation model of connection number is established,and the Euclidean distance ideal solution and the improved method of its weight are introduced.Then take the ten groups of flood encounter combination under the three level years of high,low and normal flow as a scheme set respectively,through the calculation of the connection number between the statistical index of flood encounter and evaluation levels,the matrix of flood encounter magnitude is established,and the ordering of the schemes for pros and cons is made.It is considered that in the background of high and normal flow years,attention should be paid to the flood of Jinsha River and the main stream of Yangtze River encountering at Yichang station,and reinforce the optimized joint flood control operation of Xiluodu-Xiangjiaba-Three Gorges cascade reservoir group in the main stream.While under the background of low flow years,attention should be paid to the flood encounter problem of Minjiang River and Jialing River,and flood resources should be fully utilized to ensure the beneficial demand of the Yangtze River,such as shipping and water supply.