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<br />-21- <br /> <br />Water Surface Computations <br />Water surface profiles along Gore Creek have been determined for <br />each discharse using the cross-section of the channel, a channel rough- <br />ness coefficient and an energy balancing procedure known at the " step- <br />wise backwater method". Where supercritical flows existed, the critical <br /> <br />depth was substituted. The channel roughness values have been varied <br />with depth and along the section. <br />Description of Floodinq <br />Gore Creek experiences both natural flooding and flooding caused <br />by flood plain encroachment. Natural flooding has historically occurred <br />in the meadows where the main channel is shallow. The flood waters <br />forced out onto the meadows are typically shallow, low-velocity flows <br />which may cause moderate deposition of sediment and debris. Additionally, <br /> <br />beaver dams have caused "natural" constrictions which further flooded <br /> <br />these meadows. Secondly, some areas along Gore Creek suffer extended <br />flooding due to constrictions in the channel size at bridges or where <br />the banks have been modified for construction. The consequences are <br />higher water surfaces upstream of the constriction, higher velocities <br /> <br />through and immediately downstream of the constriction and increased <br />erosion/sedimentation/debris problems. <br />An overview of the basin and also detailed flood information is <br />included in Plates 1 through 25. Plate 1 provides an index to flooded <br />area maps and delineates the sub-basins. Plates 2 through 19 delineate <br />the 100 year return period flooded an',,_ Plates 20 through 24 show the <br />10 and 100 year flood profiles. Plate 25 shows cross-sections typical <br /> <br />of much of the Gore Creek chdnnel. <br /> <br />. <br /> <br />. <br />, <br />-I <br />'j1 <br />, <br />" <br /> <br /> <br />-22- <br /> <br />. <br /> <br />The most serious of the flooding problems are: II the house in <br />the low West Vail meadow at Section 5; 2) above the bridge at Ptarmigan <br />Section 12; 3} the Vail Village area upstream of the Willow Bridge <br />Road foot bridge; 4) above the Bridge Street foot bridge; 5) the <br />bridge below the confluence of Gore and Black Gore CreekS at cross. <br />section 64, and 6} at the confluence. <br />The yard of the house at Section 5 in the West Vail meadow area <br />is subject to shallow flooding under existing conditions. However, <br />the real hazard to this residence is the possibility of Gore Creek <br />returning to a previous alignment which could increase both levels <br />and velocities of the flood water adjacent to the house. <br />The bridge at Ptarmigan (cross-section 12) causes flooding of <br />the foundation on the closest upstream condominium with some potential <br /> <br />for erosive damages. <br />Flooding above the Willow Bridge Road foot bridge extends from <br />thebridgebackto8ridgeStreet. Flooding occurs at the Covered <br />Rridg~ Stor~, th~ r.reek~ide Buildino and at the Vail Center A and B <br />condominiums. Figures IV-2 through IV-6 show flooding elevations in <br /> <br />these areas. <br /> <br />. <br /> <br />The Bridge Street foot bridge into the village causes moderate <br />backwater flooding against the Gallery Building which will probably <br />result in basement flooding with the possibility of erosion. The <br />extent of this flooding may be seen in Figures IV-7 and IV-S. <br />The bridge below the confluence at Section 64 has too low a <br />clearance as seen in Figure 12. An alternate to replacing this <br />