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~23~ bridge with a larger bridge is to gr~de the north bridge approach lower to allow overflow at a lower flood elevation. The erratic flooding at the confluence of Gore and Black Gore Creeks is due to poorly defined, unpredictable channel location. A very higl1 discharge could "choose" an alignment anywhere within the shown flood plains with probable high velocities. Photographs of other minor flooding points are also included. Figure IV~l shows a utility line along the bridge at Section 3 which could be damaged during a storm. There are several other utility lines, both sewer and water, crossing Gore Creek which may possibly be damaged. Figure IV~ll shows the shallow flooding at the starter house of the Town of Vail Golf Course. Shallow depths and slow velocities are typical of flooding in the golf course. Plate25,Section49.4.1, . shows a Golf Course section. Although the extent of flooding is very important, the velocity distribution within the flooded area and the duration of flooding are very important in describing the hazards and potential damage. Water velocities in the main channel of Gore Creek vary from five to fifteen feet per second. Away from the main channel in the overbank areas, depths are shallow and the velocities will be one to four feet per second. While the overbank flooding velocities may present a serious hazard to persons, they are usually not so high as to cause significant structural damage to the shallowly flooded building nor .i extensive erosion in the meadows. However, the main channel velocities will result in erosion and transportation of sediment. including boulders weighing hundreds of pounds. "'i ,:," .c, ~24- . The results of the sediment (up to boulders) and debris transport can be undermined foundations, structural collapse or damage and deposition of thick layers of boulders, gravels, sands and silts in areas where slower velocities exist (such as the meadows). The duration of the flooding is especially important where erosion occurs. These erosive forces may cause the relocation of the main channel during floods, especially at curves and oxbows in the meandering portions of the creek. For this reason, a 100 year flooded area map for Gore Creek may represent a different level of hazard to properties near and within its limits than would a similar map for a slow-moving stream or river. Examination of properties for flood hazard should include both a comparison of the site elevations with the 100 year flood elevation and the susceptibility of the property to erosion or deposition. Debris The flooding in many areas extends into the wooded areas of the meadows and streamsides. The results are that any floatable or erodable debris may be picked up and carried downstream. In addition to this . natural debris, the smaller bridges which may be washed out during these floods present a significant hazard to downstream bridges. The bridge debris may restrict not only water passage efficiency of any downstream bridges, but may also act as a battering ram to collapse or weaken these other bridges. Consequently, any fragile bridges or large potential debris in the upstre~rn reaches constituteS a re,atively significant hazard to e~ch structure below it. -."