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<br />2 <br /> <br />... <br /> <br />.. \ ;, <br /> <br />Photography Acquisition <br /> <br />Three sources were used to obtain aerial photography of the study <br />sites. Initially, the National Cartographic Information Center <br />(NCIC) of the U.S. Geological Survey (USGS) was contacted to <br />obtain a listing of the aerial photography available for Colorado <br />and Utah. This information was obtained in microfiche form and <br />organized according to a geographic grid system. Photography is <br />described for an area whose extent, both longitudinally and <br />latitudinally, is 7 1/2 minutes. From these listings, projects <br />of ,suitable scale (1:20.000 to 1:40,000 range) and date were <br />studied to ascertain the extent of their coverage and quality. <br />Locally available project photo mosaics and photo indexes for <br />USGS photography and Bureau of Land Management (BLM) photography <br />were used to select the appropriate exposures that covered the <br />reach of stream of interest. Topographic maps outlining the area <br />of interest were sent to the U.S. Department of Agriculture <br />(USDA) Aerial Photography Field Office to obtain photographs from <br />this source. Appendix A contains the addresses of the photo <br />source agencies and a listing of photos obtained from these <br />sources. \ <br /> <br />Analysis <br /> <br />Data for each PHABSIM site collected during field measurement of <br />the site was considered along with stereo-pair analysis of the <br />channel conditions. The extent and status of the field data <br />available for each site varied; we used all available field data, <br />as of September 1984, to aid in our photointerpretation. Also, <br />we estimated the discharge at the study site on the photo date by <br />using flow records for the nearest USGS stream gaging station(s}. <br />