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Cross Section Surveys Green River Cross section surveys were performed for all eighteen cross sections. The cross sections were surveyed in 1997 at approximately 18,000 cfs, 4500 cfs, and 2500 cfs for the SR, SN/IM, and SL sites respectively. All cross sections, with the exception of the SR cross sections, were re-surveyed in 1998 at approximately 13,000 cfs. Cross section endpoint elevations were confirmed by running internal level loops between LEP B&C and REP B&C at each section. The elevations for all the cross sections closed within 0.02` based on the internal closures. Future surveys are recommended at these locations to monitor changes and potential responses to levee removal activities. Gunnison River Cross section surveys were performed for the GRBC14S site on May 21St, 1997. A discharge measurement was also performed that day. The corresponding dischar~e was 9300 cfs. The river cross sections for the Dad's Flat site were surveyed on May 30th and 315, 1997. The discharges at the Gunnison River near Grand Junction for those days, assuming a lag time to the site, were approximately 8500 cfs to 9000 cfs. No cross section surveys were performed in 1998. The cross section data and plots can be found in the accompanying technical report. Colorado River Cross section surveys were performed for the CRBR181 N site on September 9th, 1997 and again on July 6th, 1998. The corresponding flows at the Colorado River below Grand Valley Diversion near Palisade, Colorado for those days were 2200 cfs and 5800 cfs, respectively. The cross section plots indicated no significant changes in the cross sections for that range of flows. • Topographic Surveys In addition to the river cross sections, topographic surveys were also performed at the four sites. Initially, survey control points were established in order to shoot the topography of the bottomland and river. Fence posts, and B&C's, similar to those described above, were set into the ground at enough locations to be able to map the extent of the bottomland and river. At each control point, existing bench marks from other bottomlands or local highway benchmarks were located in the vicinity to establish vertical control. Horizontal control was assumed for all four sites. The Bureau of Reclamation (USBR) surveyors were contracted to locate property lines and local control relative to the FLO control points. This information has been added to the FLO mapping. The total station was used to shoot two or more existing benchmarks to establish horizontal and vertical control for the control points. Where possible, level loops were run from the benchmarks to the control points to assign a more accurate vertical elevation. The level loops were run to at least one of the control points for each bottomland. The accuracy of topographic mapping was verified by checking the trigonometric elevations of the endpoints shot by the total station versus the elevations established by running differential level loops from the control points. None of the vertical data had to be adjusted. The maps are presented with 2-foot contours. Access roads and structures are displayed to indicate when these areas are inundated by existing or proposed flooding. The topographic maps for each site are presented in Chapter III, on 11" x 17" sheets. Larger maps are available upon request. n LJ 2-2