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Grams and Schmidt 13 total length. Fine-grained alluvium is next in abundance, occuring along about 30 percent of the bank length. An additional 14 percent is debris-fan material, 11 percent is gravel, and 4 percent is mixed alluvium (Table 2). Conversely, fine-grained alluvium is the dominant material in meandering reaches, occuring along 72 percent of the bank length. Bed material at the surveyed cross sections, the portion of the bed exposed at low discharge, and bore-hole data indicate that within the study area the river does not flow directly on bedrock. Fine-grained alluvium is the dominant bed material at 39 percent of the 67 surveyed channel cross sections in the study reach, and is gravel at 33 percent of the cross sections. A mixture of fine-grained alluvium and gravel covers 25 percent of the cross sections and the remaining 3 percent have boulder and talus beds (Table 2). Fine- grained alluvium is more abundant in the meandering reaches and less abundant in the canyon reaches (Table 2). Despite the abundance of bedrock and talus on the banks, rarely is the bed comprised of these materials. Bore-hole data indicate that the channel consists of river-deposited alluvium inset into the bedrock gorge. Drill holes completed for dam-site surveys at the entrance to Lodore Canyon (Wooley, 1930) and in Whirlpool Canyon (Merriman, 1941) show about 45 m of sand and ,gravel overlying bedrock. The dam-site survey above the mouth of Split Mountain Canyon shows 12 m of alluvium over bedrock (Merriman, 1940). The measured depths to bedrock are shown on the longitudinal profile in Figure 6. Individual rocks photographed in 1871 are still present in the same locations at river level (Stephens and Shoemaker, 1987) indicating there has been no significant shift in mean bed elevation during the past century. The cross-section data and the bore-hole data support the observation that nowhere does the bed of the river flow in contact with bedrock despite the occurrence of bedrock as bank material. 6.2.2 Coarse-Grained Alluvium Debris fans are most abundant in the canyon reaches. The total number of fans, fan frequency, and average d~l>ris fan area are listed for each reach in Table 3. The