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Grams and Schmidt 18 Reach average gradient (5-km moving average) is plotted against bedrock resistance at each cross section in Figure 11a. The steepest reaches always occur in highly resistant rock, but low-gradient reaches occur in rock of all degrees of resistance. The same data are shown as weighted averages for individual canyon and meandering reaches in Figure lIb. In Lodore and Whirlpool Canyons, the Uinta Mountain Group quartzite lines the channel in the steepest reaches and the Paleozoic formations (except Weber Sandstone) are associated with reaches of intermediate gradient In Split Mountain Canyon, however, the Paleozoic rocks are associated with gradients steeper than occur elsewhere in any of the canyons, even those of more resistant formations. The Weber Sandstone, Mesozoic rocks, and Tertiary rocks of the park reaches are all associated with low channel gradients. Thus slope is not well correlated with resistance ona short-reach scale of about l-km but is better correlated on a reach-average scale. The coincidence of debris fans and high-gradient reaches is also shown on Figure 6. Debris fan frequency is plotted against channel gradient in Figure 12. High debris-fan frequency is exhibited in all high-gradient reaches, and fan frequency is low in all low- gradient reaches. 6.4 Channel Geometry Channel geometry is similar for reaches of similar geology. The ratio of channel width to channel depth at post-Flaming Gorge Dam bankfull discharge (122 m3s-1 above the Yampa River confluence and 480 m3s-1 below the confluence) is shown in Figure 13. The reach-averaged geometric parameters of channel top width, cross-sectional area, and width-to-depth ratio are all less in the canyons than in the meandering reaches (Table 5). The coefficients of variation are large for most parameters. This variation arises from local variations in channel characteristics. Despite this local variability, reach-length trends are evident. Moreover, the coefficients of variation decrease when the sampled subset for each parameter is stratified to include only geologically-similar reaches (Table