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2. SUMMARY OF 1997/1998 FIELD DATA COLLECTION EFFORT Establishment of River Cross Sections Green River In order to develop stage/discharge relationships and/or a hydraulic model for the river adjacent to the bottomland sites, river cross sections had to be established. Six new river cross sections were established in each reach adjacent to each bottomland site. -The cross sections were selected with respect to local hydraulic controls and anticipated levee removal areas: The cross sections were established with endpoints which consisted of a marked 2 inch aluminum survey cap mounted to a 3-foot length of rebar and driven to ground .level on each side of the river. Typically, the cross sections were set to extend beyond any existing levee located at the site. In front of the bar and cap (B&C), towards the river, atag-line-post (TLP, a T-fence post), was installed to mark the location of the endpoint and to attach atag-line while surveying the cross section. The B&C's on each side of the river were surveyed for elevation and horizontal position with a total station. Survey control sheets and cross section survey data sheets can be found in the accompanying 1998 Floodplain Habitat Restoration Technical Report (FLO, 1998). In addition, level loops were run from a nearby vertical control point to establish a more accurate elevation for the endpoint B&C's and TLP's. For the GRSL288N bottomland, a level loop was run from the upstream most Horseshoe Bend cross section (HB-4) and continued to the downstream most Bonanza Bridge bottomland. This tied in the three bottomlands to the same vertical control. The Bonanza Bridge data has not been modified, however. It was preferable to maintain the consistency in an already established monitoring effort at the site. For the GRSN303W bottomlands, a level loop was run to establish vertical data from cross sections in the • Escalante reach, approximately two miles upstream. At the SR site, vertical control was established from a local highway benchmark. At some point, it would be advantageous to tie all the river cross sections which have been established from Split Mountain to Desolation Canyon to the same horizontal and vertical control. In addition, with the placement of approximately fifty more cross sections, the gaps between bottomland study reaches could be filled, and a full scale monitoring program could be established to gain a better understanding of the geomorphological trends in this biologically important reach of river. Gunnison River For the Gunnison River sites, five and six river cross sections were established for the GUBC14S and Dad's Flat sites, respectively. At the GUBC14S site, vertical control was brought in from a State Highway Department right-of-way marker. The 3-inch brass cap was located on the south side of Highway 50, east of Willow Bend Road, near mile marker 40. The elevation on the cap was 4695.32 at STA 520+00.0. Horizontal control was assumed 10,000, 10,000. For the Dad's Flat site, vertical and horizontal controls were assumed, as no benchmarks were located in the vicinity. Colorado River At the BO/BR site along the Colorado River, five river cross sections were established. For vertical control, a level loop was brought in from local Federal Emergency Management Agency (FEMA) benchmark RM48. Horizontal control was assumed 5,000, 5,000. • 2-1