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<br />Grams and Schmidt 4 <br /> <br />geology on channel geometry is sufficiently strong that a 'typical' cross section can be <br />defmed for reaches of similar river-level geology. <br />Although descriptions and classifications of fluvial bedforms are common (Church <br />and Jones, 1982; Jackson, 1975), few schemes have specifically discussed bedforms in <br />deep canyons. Baker (1984) described a classification of gravel bedforms in bedrock <br />systems that emphasizes local control features, such as tributary fans, and the hydraulics <br />of extreme floods. Howard and Dolan (1981) classified deposits in Grand Canyon based <br />on grain size: (1) bouldery debris fans that occur at the mouths of most tributary streams <br />and are reworked by large floods on the Colorado River, (2) main-stem cobble bars <br />transported only during floods , and (3) fine-grained alluvium deposited in eddies and <br />along the channel margins and which are transported primarily as suspended load. These <br />aspects of the fluvial geomorphic organization of canyon-bound rivers transcend local <br />variations in lithology. <br />Schmidt and Graf (1990) and Schmidt (1990) focused on the details associated <br />with depositional zones created by debris fans, and described patterns of alluvial <br />sedimentation and erosion in eddies and channel-margin deposits. Within eddies, Schmidt <br />(1990) distinguished between separation bars, formed near the point of flow separation, <br />and reattachment bars, formed near the flow reattachment point. The sedimentology and <br />stratigraphy of these bars have been described by Rubin and others (1990), Schmidt and <br />Graf (1990), and Schmidt and others (1993). Schmidt and Rubin (1995) argued that the <br />assemblage consisting of debris fan, upstream backwater, and downstream eddy and <br />gravel bar comprise the fundamental geomorphic unit in canyons with debris fans and <br />termed this unit the fan-eddy complex. For river systems on which debris fans are typical, <br />patterns of sedimentation and erosion are largely determined by debris fan geometry, <br />distribution, and ultimately, the frequency of fan-forming events. Sedimentology of <br />debris fans, frequency of fan-forming debris flows, and the effects of debris fans on rapids <br />were discussed by Webb and Q.thers (1989) and Melis and others (1993). The hydraulic <br />