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<br />active bank to bank and vegetation encroachment on the bars is minimal (FLO, <br />1994). The sand-bed channel is confined in some reaches by valley bedrock or <br />alluvial hills. <br /> <br />Yampa River Flows and Channel Morphology <br />The Yampa River is the only major tributary in the Upper Basin whose flows <br />have not been substantially altered by water resource development involving <br />mainstem channel impoundment or significant water diversion. As such, the <br />Yampa River still exhibits the basic diversity and integrity of habitat associated <br />with highly variable flow conditions and sediment loads. <br /> <br />Downstream of the Yampa River and Little Snake River confluence is an <br />8-km long, sand-bed reach in Deerlodge Park. When the river enters Yampa <br />Canyon, it begins a steep and tortuous descent of 72 km to a confluence with the <br />Green River in Echo Park. The canyon channel morphology is dictated by geology <br />and there are few areas of canyon bottomland floodplain. Much of the Yampa <br />River in Yampa Canyon has boulder or bedrock substrate. The sand load from the <br />Little Snake River and upstream Yampa River passes through the canyon with <br />minimal opportunities for storage within the active channel. <br /> <br />Yampa Canyon provides a diverse variety of fish habitat ranging from runs <br />in cobble riffles, boulder rapids, eddies, sand-bed pools, deep boulder holes and <br />backwater habitat. In the lower half of Yampa Canyon, the river follows ancient <br />meanders incised in soft Weber sandstone. Reaches of cobble substrate have <br />evolved into a riffle-pool sequence related to river bend constrictions and canyon <br />expansions. The cobble bars are energy dissipating structures that promote <br />overall channel stability (O'Brien 1984). The cobble riffles around the bars are <br />relatively free of sand despite the large sand load supplied by the Little Snake <br />River. The peak sediment load lags the water discharge peak by several days in <br /> <br />25 <br />