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FLOOD00653
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Last modified
11/23/2009 1:21:37 PM
Creation date
10/4/2006 9:24:47 PM
Metadata
Fields
Template:
Floodplain Documents
Designation Number
253
County
Boulder
Community
Jamestown
Title
Flood Insurance Study - Jamestown, Boulder County, Colorado
Date
1/1/1983
Designation Date
3/1/1986
Floodplain - Doc Type
Floodplain Report/Masterplan
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<br />Flood profiles were drawn showing computed water-surface elevations <br />to an accuracy of 0.5 foot for floods of the selected recurrence <br />intervals (Exhibit 1). <br /> <br />Roughness coefficients (Manning's "nll) were estimated by field <br />investigation using a paper by V.V. Golubtstov (Reference 5). <br />The roughness values for the main channels ranged from 0.03 to <br />0.75 and for the overbanks from 0.06 to 0.1. Water-surface eleva- <br />tions for James Creek were.started at normal depth. Water-surface <br />elevations for Little James Creek and Unnamed Tributary to Little <br />James Creek were started at their respective confluence elevations <br />resulting ftom coincident discharges. <br /> <br />., <br /> <br />" <br /> <br />., <br /> <br />All elevations are referenced to the National Geodetic Vertical <br />Datum of 1929 (NGVD). Elevation reference marks used in the <br />study are shown on the maps. <br /> <br />, <br /> <br />4.0 FLOOD PLAIN MANAGEMENT APPLICATIONS <br /> <br />The National Flood Insurance Program encourages State and local govern- <br />ments to adopt sound flood plain management programs, Therefore, each <br />Flood Insurance Study includes a flood boundary map designed to assist <br />communities in developing sound flood plain management measures. <br /> <br />4.1 Flood Boundaries <br /> <br />In order to provide a national standard without regional discrimi- <br />nation, the 100-year flood has been adopted by the Federal Emergency <br />Management Agency as the base flood for purposes of flood plain <br />management measures. The SOO-year flood is employed to indicate <br />additional areas of flood risk in the community. For each stream <br />studied in detail, the boundaries of the 100- and SOO-year floods <br />have been delineated using the flood elevations determined at <br />each cross section; between cross sections, the boundaries were <br />interpolated using topographic maps at a scale of 1:1200, with <br />a contour interval of 2 feet (Reference 6). <br /> <br />,- <br /> <br />Flood boundaries for the 100- and SOO-year floods are shown on <br />the Flood Boundary and Floodway Map (Exhibit 2). In cases where <br />the 100- and SOO-year flood boundaries are close together, only <br />the 100-year flood boundary has been shown. Small areas within <br />the flood boundaries may lie above the flood elevations and, <br />therefore, not be subject to flooding; owing to limitations of <br />the map scale, such areas are not shown. <br /> <br />i; <br /> <br />4,2 Floodways <br /> <br />.i <br /> <br />Encroachment on flood plains, such as artificial fill, reduces <br />the flood-carrying capacity, increases the flood heights of streams, <br />and increases flood hazards in areas beyond the encroachment <br /> <br />, <br /> <br />10 <br />
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