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<br />North Creede on East Willow Creek. Five additional cross-sections were measured upstream of <br />the Commodore Mine, but base elevations were determined using the USGS topo maps due to <br />the extreme elevation changes. A total of 1077 points were measured within the cross-sections. <br />Survey stakes, painted orange on top, were placed at the end-points of these cross-sections and <br />most can still be located in the field for observation or additional surveying during the <br />construction phase. Figure 2.1.3 displays the locations of survey measurements (except for the <br />points upstream of the Commodore). <br /> <br />Survey elevations were tied to a rebar rod placed by the U.S. Forest Service near the Commodore <br />Mine tunnel. This rod was tied by the Forest Service to a USGS monument near Deep Creek. <br />After surveying from the flume entrance to the Commodore Mine, the survey loop was closed <br />and resurveyed back to the flume. An error of less that I-foot was found, an adequate accuracy <br />given the channel slopes. The topography at the flume appeared to be about 3.5 feet higher than <br />topography displayed near the flume entrance in the 1986 CWCB Creede Flood Hazard Report <br />(Mullen, 1986). This topography was reported to be from a 1971 map of the City of Creede. <br />The discrepancy between the survey datum used for the 1971 map and the Forest Service rod is <br />not known, but topography may have to be adjusted slightly to match studies below the flume <br />entrance. The location of the Forest Service rebar rod is also shown in Figure 2.1.3. <br /> <br />High-resolution color aerial photography was taken to facilitate the contouring of topographic <br />features. Color photos were taken primarily of the floodplain areas from the flume entrance to <br />above the Amethyst Mine on West Willow Creek and to about 4000 feet above North Creede on <br />East Willow Creek. Individual photos were geo-referenced to lower resolution DOQQ photos <br />and mosaiced into larger images. Final mosaiced images have a resolution of about 0.38 meters <br />(1.2 feet). High-resolution topography was drawn on the aerial photos using the survey points <br />using a 2-foot contour interval. Figures 2.1.4a through Figure 2.1.4d display the floodplain <br />topography on top of the color aerial photos. <br /> <br />2-4 <br />