Study On The Information Extraction And Evolution Of Old River Channel By Using RS Data In East Of Chaohu Lake

Chaohu-lake basin is located in the middle of Anhui Province. Southeast of the area is close to Yangtze River, north of the area is watershed areas of Yangtze River and Huaihe River, northeast of the area is Chuhe drainage basin. with the water system belongs to left bank of Yangtze River. The rivers from Chaohu Lake inflood into Yangtze River distributing in the eastern of Chaohu-lake basin ,the river system from Chaohu Lake inflood into Yangtze River have occurred a very significant change due to the natural environment and human activities.This paper studied and discussed with two aspects contents: One is the old river system information extractiom means from SPOT data by remote sensing numeral image analysis processing; The other is, it emphasize, River system vicissitude characteristic from Chaohu Lake inflood into Yangtze River, and the reasons of the River system vicissitude with the comparative study of RS images, relief maps, Geological map, historical preference, chorography, field survey and etc. We can come to the conclusions as follows:(1) For SPOT data has rich information, through study on spectral characteristics of the different types of old riverway type, because of the SPOT data in study area has special time features, we establish information extraction model based on the spectral characteristics in the farmland mask image which have exclude other information interference, and Build process of the old riverway information extraction from Supervised Classification to Farmland Mask to Primary Component Analysis to Underground Old Riverway Information Extraction to Information Merger to Old River System Extraction Image.(2) There is a big old river system in west of the Zhegao River basin in Geological history. According to the Chaohu lakeshore changes and historical preference study speculates that: the old river have two possible ways to inflood into Yangtze River: One is it go through the Chaohu lake from north to south, linked to the Mawei River ,White Lake, inflood into Yangtze River by Xi River. the other is it go through Yuxi River than inflood into Yangtze Riverfrom north to south.(3) Historical preference Show that Zhegao River is one branche of Yuxi River in history stage. Because of faulted structure causes the lakeshore collapse serious, Zhegao River become one of branches of Chaohu Lake not late than Song Dynasty.(4) Overall view , the river system from Chaohu Lake inflood into Yangtze River Changes generally follow the migration from west to east direction. The old riverway in Zhegao River basin show that its Swing from west to east ,the rivers in east of Chaohu Lake basin inflood into Yangtze River Changes from Xi River to RuXu River than modern Yuxi River, and estuary RuXu have occurred three major diversion also have basically gone through West to East changes, further more, the Chaohu Lake basin has siltation in west and collapse expand in north, south and east.(5) The influence factors of river system variance include geological tectonic,climate, changes of Chaohu basin,and human activity. Geomorphy is the elementary factor, and climate influence water and sand offered by river basin, geological tectonic control whole structure of river system ,and have the most far-reaching impact on river system variance, human activities on the recent change in the river course have a significant impact. Structural movement of earth crust from west to east cause the riverway move from west to east.