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<br />. \ . <br /> <br />.~ ~OLO::OO ~IvVER BASI'N STUOY <br />STREAM CHANNEL STABILITY AT PHABSIM SITES <br /> <br />~~" <br />o7z92- <br /> <br />. "\ <br /> <br />Introduction <br /> <br />The objective of this portion of the stu~y is to evaluate the <br />geomorphic stability of each PHABSIM study site. The approach <br />used involved examination of stream channel morphology for each <br />study site from aerial photographs. The comparison of channel <br />conditions was limited to two time periods for each site. The, <br />date of the photography depended on several factors including the <br />availability of photographs of a suitable scale and the histor- <br />ical habitat reference period for each river basin. Under study <br />task 7.1, the Colorado River Fishery Project (CRFP) project <br />leader has identified the following time periods as reprensen- <br />tative of historical conditions which were satisfactory for the <br />endangered Colorado River fishes: <br /> <br />Colorado River <br />Green River <br />Gunnison River <br />White River <br />Yampa River <br /> <br />1950 <br />1960 <br />1960 <br />1982 <br />Present (1984) <br /> <br />Prior to these time periods, water development was minor within <br />the respective basins. Aerial photography taken near these dates <br />was used to define the historical channel morphology for each <br />study site and compared to channel conditions viewed on recent <br />aerial photography. <br />