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<br />3.2 Hydraulic Analysis <br /> <br />The August 22, 2003, hydraulic analyses of the Colorado and Eagle River <br />computed the water-surface elevations (WSELs) for floods of the selected <br />recurrence intervals using the USACE HEC-RAS backwater computer program <br />(Reference 18). A total of 471 cross sections were secured from topographic <br />mapping and field surveys. <br /> <br />One bridge is located within this study reach of the Colorado River. The bridge <br />is a cable and wood bridge used for livestock to cross the river. A total of <br />42 bridges are located within this study reach of the Eagle River. There are four <br />old concrete arch bridges on the Eagle River: an abandoned bridge at Gypsum, <br />an abandoned bridge between Eagle and Wolcott, Highway 131 Bridge at <br />Wolcott, and an old bridge with a new deck on the County Road at Minturn. <br />These bridges have limited hydraulic capacity and provide little. or no freeboard <br />during a IOO-year flood. Of these four bridges, only the Highway 131 Bridge is <br />not overtopped in a flood. The Gypsum Bridge and the bridge between Eagle <br />and Wolcott have failed structurally and are no longer used for vehicular traffic. <br /> <br />Detailed field survey measurements were taken along the bridge decks, and at <br />every cross section upstream and downstream of the bridges. This survey <br />information was completed between May and October of 2002. <br /> <br />The cross sections for the Eagle River near Minturn and Eagle River near <br />Red Cliff, Fryingpan River, Tayior Creek, and Turkey Creek were obtained by <br />field surveys. Cross sections for the backwater analyses of Brush Creek, <br />Reach 1, were also obtained from field surveys. Cross sections for Brush Creek, <br />Reach 2, were obtained from topographic maps with a contour interval of 2 feet <br />(References 19 and 20). In undeveloped areas, field surveys were supplemented <br />using aerial photographs (Reference 21). All bridges and culverts were field <br />checked to obtain elevation data and structural geometry. <br /> <br />Cross sections for Gore Creek and Gore Creek Tributaries were cut from the <br />topographic mapping provided by the Town of Vail. The Town of Vail <br />contracted with Peak Land Surveying to provide survey data for all crossing <br />structures within the study reaches. The February 1999 Sato work maps used <br />this topography. Revised work maps dated June 6, 2003, were provided to show <br />new locations of cross sections (Reference 22). In April 2003, the Town of Vail <br />provided updated survey data for some bridges, walls, and berms along Gore <br />Creek. The additional data included revised survey information for <br />Circle K Bridge, Ford Park Covered Bridge, and Ford Amphitheater Bridge and <br />new survey information that identified Nugget Lane and the Donavan Park foot <br />bridge. Information on the Chammonix Lane culvert along Buffehr Creek was <br />also revised. This information was incorporated into this study. <br /> <br />A total of 112 cross sections secured from topographic mapping and field <br />surveys were analyzed for the hydraulic analysis of the Roaring Fork River. <br />The locations of these cross sections are shown by reference point on the flood <br />maps and the flood profiles. <br /> <br />24 <br />