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<br />. <br /> <br />. <br /> <br />include an aerial photographic analysis of the Ruby-Horsethief Canyon <br />reaches of the Colorado River. Similar questions regarding the extent <br />of historic changes in channel morphology apply to the Ruby-Horsethief <br />Canyon reaches, but this reach is less directly influenced by human <br />settlement. We have demonstrated the utility of a GIS-based approach in <br />evaluating the significance of changes within the 15- and l8-miles <br />reaches and it is straightforward to extend this work into the Ruby- <br />Horsethief Canyon reaches. <br /> <br />III. Study Goals, Objectives. End Product <br /> <br />A. Goals and Objectives <br /> <br />1. Continue series of field measurements at specific sites to <br />predict how side channels change in response to different flow <br />and sediment transport conditions. <br /> <br />2. Quantify historic changes in channel morphology in the <br />Ruby-Horsethief Canyon reaches of the Colorado River. <br /> <br />B. End Product <br /> <br />A report summarizing the spring and summer measurements at specific <br />field sites will be prepared. Included in the report will be data <br />summarizing changes in channel morphology in relation to flow and <br />sediment transport patterns. In addition, the report will include <br />maps of historic channel change within the Ruby-Horsethief Canyon <br />reaches. <br /> <br />IV. Study Area <br /> <br />The Colorado River from Grand Junction to the Westwater Ranger Station. <br /> <br />V. Study Methods/Approach <br /> <br />This work will be undertaken as a collaborative effort between <br />biologists from the FWS field office in Grand Junction and <br />geomorphologists from the University of Colorado. Specific methods used <br />to meet the above goals and objectives are as follows: <br /> <br />1. Field studies: flow. sediment transport and cross-section <br />measurements will be continued at the 4 backwater sites established <br />in 1993. These sites are similar in that each is formed by the <br />deposition of a lateral bar that forces some of the flow down a side <br />channel. The side channels differ in the amount of flow they carry, <br />presumably because they are at different stages in their evolution. <br />In 1993 we surveyed cross sections at the upstream and downstream <br />ends of the side channels. Typically, the upstream entrance to a <br />side channel is made of coarse gravel that can be moved only at high <br />flow. We focused attention on these areas because the elevation of <br />the upper end controls the amount of flow that can enter the side <br />channel. The lower end of the side channel is also of interest <br />because if flow is not sufficient to flush sediment through the side <br />channel. the lower ends can become filled in thus limiting access <br />for the fish. <br /> <br />2 <br />