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-21- lV._-S.I!A"!.NJJ FLO.!U_HARACTER1STlCS AND FLOODING Channel Character The characteristics of Gore Creek vary from steep, relatively straight and rough in the reaches above the confluence of the Gore and Black Gore Creeks to shallow and slopes with meanders in the valley meadows then to boulder-strewn, incised channel from west of Vail to the confluence with the Eagle River. Figures IV-l through IV-12 show channel characteristiCS from West Vail up to the con- fluenceofGore and Blad Gore Creeks. The eastern portions of the valley receive direct sunlight most of the year. Kowever, some of the more incised sections are shadowed much of the time, which is conducive to ice jamming in these narrow, cooler sections. Channel surface roughness (used for flow friction computations) varies from n ~ .03 in the meadows to n ~ .08 for shallow flows in the bouldered portions of Gore Creek. The slopes within the channel (vertical drop divided by the horizontal run and expressed as a per- cent) vary from four percent to seven percent above the confluence of Gore and Black Gore Creeks, then 0.5% to 3X in the meadows along the golf course and then 0.2% to 1.5% near the Eagle River. Elevations of the valley and chann~l have been determined in critical locations from field surveys and otherwise from both field surveys and the two foot interval orthographic contour maps prepared for the Town of Vail by Falcon Air Maps. Water Surface Computations Water surface profiles along Gore Creek have been determined for each discharge using the cross-section of the channel, a channel rough- ness coefficient and an energy balancing procedure known at the "step- wise backwater method". Wheresupercritical flowsexisted,thecritical depth was substit~ted. The channel roughness val~es have been varied with depth and along the section. Description of Floodinq Gore Creek experiences both natural flooding and flooding caused by flood plain encroachment. Natural flood1ng has historically occurred in the meadows where the main channel is shallow. Thefloodwaters forced out onto the meadows are typically shallow, low-velocity flows which may ca~se moderate deposition of sediment and debris. Additionally, beaver d<lms have caused "natural" constrictions which further flooded these meadows. Secondly, some areas <l10n9 Gore Creek suffer extended flood1ng due to constrictions in the channel size at bridges or where the banks have been modified for construction. The consequences are higher water surfaces upstream of the constriction, higher velocities through and immediately downstream of the constriction and increased erosion/sedimentation/debris problems. An overview of the basin and also detailed flood information is included in Plates 1 through 25. Plate 1 provides an index to flooded area maps and delineates the sub-basins. Plates 2 through 19 delineate the 100 year return period flooded area. Plates 20 through 24 shOw the 10 and 100 year flood profiles. Plate 25 shows cross-sections typical of m~ch of the Gore Creek channel.