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<br />Mineral Bottom <br />The Mineral Bottom study reach is located in Labyrinth Canyon, which is <br />approximately 65 km below the town of Green River (Fig. 1). The river at the <br />study reach is incised deeply into the Colorado Plateau resulting in a narrow <br />alluvial va1l4~y and a fixed meander channel pattern. The channel is generally <br />narrower than at Ouray. The average width-to-depth ratio for the bankfull <br />channel is only 30 for the Mineral Bottom reach as compared to 41 at Ouray. The <br />gradient is .00019 m/m which is slightly greater than at Ouray. The substrate <br />consists of silt and sandi however, silt is more prevalent than at Ouray. This <br />year exposed sand was found only on the highest points of the highest bars, in <br />moderate to high velocity runs and chutes and in the main channel Otherwise, <br />a veneer of silt ranging from 1 to 10 centimeters covered the sand. <br />The introduced Saltcedar and native willows have heavily invaded the <br />riparian zone in most of the study reach. Mature Saltcedar trees line the upper <br />third of the four to five meter high banks. Willows commonly occupy the zone <br />between the Saltcedar and the water surface. At Mineral Bottom it is likely that <br />vegetation does have a significant influence on channel behavior. <br />Cross,.section benchmarks were originally installed in this study reach by <br />the USFWS. In 1995 personnel from USU reoccupied the site. They added 3 new <br />cross-sections and surveyed whatever previously established cross-sections that <br />they could find. The cross-sections in existence at the start of 1996 are shown in <br />FIGURE 3. Note that the cross-sections were not evenly spaced, but were <br />positioned more closely in areas with bar activity. In October of 1996, four <br />additional CI'OSS-Sections were added to the existing eleven and a new right- <br />bench-mark was installed to reestablish cross-section 5. These are the cross- <br />sections in FIGURE 3 labeled "1996". With the additional cross-sections and <br /> <br />\ <br />reoccupation of all original cross-sections the spacing is sufficiently uniform to <br />assure the modeling resolution necessary for nursery habitat studies. This final <br />cross-section pattern is evenly spaced at approximately 1.5 channel widths and <br />extends for 3.2 river km. <br /> <br />8 <br />