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Last modified
1/26/2010 10:09:50 AM
Creation date
10/5/2006 4:29:15 AM
Metadata
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Template:
Floodplain Documents
County
Grand
Community
Granby
Stream Name
Fraser River, Tenmile Creek
Basin
Colorado Mainstem
Title
Silvercreek Floodplain Study
Date
2/1/1984
Prepared For
Grand County
Prepared By
Wright Water Engineers, Inc.
Floodplain - Doc Type
Floodplain Report/Masterplan
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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />, I <br />I <br />I <br />I <br /> <br />SECT! ON II <br />STUDY AREA <br /> <br />The study area is shown on Figure IV-2 with the specific areas of interest <br />beginning about 1/2 mile east of the confluence of Fraser River and Tenmile <br />Creek. The study continues from that line 2.5 miles upstream along the <br />Fraser River and 3.1 miles up Tenmile Creek. <br /> <br />FRASER RIVER <br />The study begins at a point approximately even with the western limits of <br />SilverCreek property. In this area the river has a very wide and shallow <br />floodplain. From the mapping it appears that there have been significant <br />changes in the channel location in the past and there are no guarantees that <br />channel meandering will not happen in the future. The average slope in the <br />lower study area (below Highway 40) is 0.6 percent. The stream bed is <br />cobble-lined with dense willow growth on the overbank. For this study an <br />"n" value of 0.035 was used for the channel and 0.08 for the overbank area. <br />The Highway 40 bridge is the only crossing in the study reach and it has <br />sufficient capacity for the 100-year flood with 2 feet of clearance below <br />the bridge low-chord. This is a large enough opening and clean design so <br />that no bridge blockage was assumed in the analysis. <br /> <br />East of the Highway 40 bridge the stream continues to meander and generally <br />has the same characteristics as the reach below the bridge. The slope <br />ranges from 0.4 percent to 0.9 percent. All the ditch crossings were <br />assumed to be sealed so there could be no flow under the highway except at <br />the bridge. There is some ponding upstream of the highway and a large area <br />of shallow flooding. The most significant cause of this is an irrigation <br />ditch which diverts from the river about 2,500 feet east of Highway.40. <br />This ditch brings a small amount of flow to the south of the main channel <br />parallel with the river. Between the river and the railroad tracks there <br />are several ponds that may have been gravel pits at one time. East of these <br />ponds, the river continues to meander throughout the floodplain and there is <br />
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