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watersheds with the highest mean elevations do not exhibit the highest average slopes. • <br />Longitudinal profiles of the longest channels in each of the five above ref erenced <br />tributaries ere shown in Figure 7-4. Review of the profiles indicates, with the exception <br />of Y-2 tributary, the profiles exhibit both concave end convex sections. Tributaries 011 <br />and Y-3 show convex sections in the upper 10 to 50 percent of the channels, while Annand <br />Draw end Y-1 tributary (longer main channels) show convex sections in those portions of <br />the main channel 35 to 60 percent of the distance from the drainage divides. The convex <br />behavior of portions of the channel profiles is largely the result of deposition, bedrock <br />control, and where significant side tributaries are confluent to the main thennels. <br />Channel erosion, concavity, will occur where the discharge is reasonably Constant, <br />allowing sufficient sediment transport capability. This can occur in the upper watersheds <br />where channel losses ere minimal and in reaches below the confluence with significant side <br />thennels. <br />Stream channel gradients for the upper and lower portions of five tributaries are <br />presented in Table 7-29. The upper reach slopes in the Annand, Y-2, end Y-3 tributaries <br />are 2.3 to 3.0 times greater than Che lower reach slopes; whereas, the upper reach slopes • <br />in the 011 and Y-1 tributaries ere only 1.15 to 1.5 times greater. This relationship ten <br />be seen on the longitudinal profile plots shorn in Figure 7-4. <br />Predicted Peek Flows. Annual mean discharges end discharges for sal act recurrence <br />intervals have been calculated for 011, Y-1, Y-2, and Y-3 tributaries, Annand Draw, Sege <br />Creek, and Grassy Creek. These drainages ere all within or immediately proximate to the <br />Yoast Nine. Discfi arges were predicted using techniques outlined in the USGS wRI Report <br />85-<086, entitled Estimation of Natural Stream Flow Characteristics in western Colorado <br />(Kircher et. el ., 1985). The techniques used to preduct discharge characteristics for the <br />six drainages involve [he use of regression relationships determined from historical <br />streamflow records in western Colorado. <br />All six drainages lie within the northwestern region as outlined by Kircher et. el. <br />(1985). The regression model developed for this region is es follows: <br />0 = eA(b1)P(bZ)E (b3 )S (b4) <br />where, B B <br />g discharge (cfs) • <br />A = drainage area (miz) <br />P = mean annual precipitation minus 10 (in) <br />90 <br />