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(Appendix B). Each set of matched photographs is accompanied by an analysis of the <br />changes in the vegetation and geomorphology visible in the image. Changes in riparian <br />vegetation, evidence of the narrowing of the active channel, the number of geomorphic <br />surfaces adjacent to the channel, and changes in substrate composition of bars and islands <br />were analyzed and summarized for each image. <br />RESULTS <br />Characteristics of the Channel <br />The majority of repeated surveys of channel cross sections show little or no <br />seasonal fluctuations in bed geometry (Fig. 2 and 3). In 11 of the 24 cross sections, bed <br />material was sand. The bed in the remaining 13 cross sections was primarily composed of <br />cobbles or gravel. Five of the cross sections spanned recirculating flow. Channel cross <br />sections containing the coarsest material were correlated with the narrowest channel widths <br />and were the most stable. Cobble-bedded cross sections in zones of downstream flow <br />often showed no seasonal change with the exception of minor aggradation in the thalweg at <br />high discharge. Sand-bedded cross sections showed the most variability with discharge. <br />Uneven bathymetric traces at high discharge indicated the occurrence of dunes which did <br />not exist at base flow. Typical depths of cross sections with uniform downstream flow <br />ranged from 2 to 5 meters at bankfull discharge. The greatest channel depths occurred <br />adjacent to zones of recirculation where depths in the thalwegs were observed as deep as 1? <br />meters at bankfull discharge. <br />Characteristics of the Banks and Shallow Bars -- Surficial Mapping <br />The banks of the Green River in the study reaches are composed of fine-grained <br />alluvium, gravel and cobbles, fine- to coarse-grained debris derived from tributaries, scree <br />that occurs as talus on the lower part of hillslopes, and bedrock. Rapids typically occur <br />where tributary-derived debris partially blocks the channel. Downstream from these <br />rapids, recirculating eddies typically occur and fine-grained alluvium, in the form of sand <br />bars, occur in these areas. Gravel bars are often located downstream from these eddies.