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<br />flow measurements were taken at the Green River gauge. When flows <br />were stabilized at each site, color infrared aerial photography was <br />acquired at an approximate scale of 1:4000. Flows were gradually <br />stepped down during the late spring and summer in order to mimic <br />the descending limb of a "natural" Green River hydrograph. <br />However, because of weather conditions the 1,430 flow was not <br />photographed in proper sequence and was actually the last flow <br />attained. <br /> <br />Field trips were taken to familiarize the photo interpreter with <br />backwater delineation and to place panel markers at specified <br />distances at each site to verify photographic scale. In addition, <br />one to three reference backwaters were selected at each flow for <br />the Island Park, Jensen, and Ouray sites, and three reference <br />backwaters were selected at three flows at the Sand Wash site. <br />Reference backwaters were measured for length and width, and three <br />depth measurements were taken at the mouth, middle, and end of each <br />backwater. <br /> <br />Aerial photographs were fitted with mylar overlays and interpreted <br />for the following classes: <br /> <br />- Riparian Vegetation <br />- Open Water <br />- Vegetated Islands <br />- Vegetated Sandbars <br />- Sandbars <br />- Bank - Backwaters <br />- Channel - Backwaters <br />- Isolated Pools <br /> <br />Because the aerial photography was at a relatively large scale <br />(1:4000), it would have been difficult to transfer the interpreted <br />classes to a standard 1:24,000 scale U.S. Geologic Survey (USGS) <br />quad, as the integrity of the larger scale data base would be lost. <br />Therefore, to maintain interpretation accuracy, pseudomap bases of <br />the same scale as the photography. were created. Roads and other <br />prominent features were delineated on photographs and compared to <br />USGS maps to insure photo scale accuracy. All roads, trails and <br />creeks on the USGS quadrangles were digitized and then plotted at <br />the same scale as the photography. These base maps were plotted at <br />the scale computed from the aerial photography for each flow at <br />each site. <br /> <br />Following transfer of photo interpretation data to pseudomap <br />overlays, the information was digitized into a GIS system utilizing <br />Geographic Entry System software. Digitization was done using a <br />Calcomp 9000 digitizing tablet linked to a Tektronix 4014 display <br />screen. Software and peripherals were run by the HP 3000 Series <br />