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<br />Flood Insurance Study Repolt Data <br />Flood Insurance Study - Cooper Slough, Larimer County, Colorado <br />Page 11 <br /> <br />4,0 FLOODPLAIN MAN,~GEMENT APPLICATIONS <br /> <br />4.1 Flood Boundaries <br /> <br />For each section studied by detailed methods, the 100- and 500- year floodplain <br />boundaries have been dHlineated using the flood elevations detBrmined at each cross <br />section. Between cross !iections, the boundaries were interpolated using topographic <br />maps at a scale of 1: 1 00 with a contour interval o'f 2 feet. <br /> <br />4.2 Floodwavs <br /> <br />It was determined in the initial c.c.a. meeting that a floodway would be delineated <br />for Cooper Slough betwe,en State Highway 14 and Vine Drive. Encroachment method <br />4, equal conveyance reduction, was used in the initial floodway run to determine the <br />floodway boundaries. Encroachment method 1 was then used at certain cross <br />sections in order to obtElin a smooth floodway boundary. <br /> <br />7.0 OTHER STUDIES <br /> <br />To ensure reliability of results of this study, the flood insurance flows would ordinarily <br />be compared with flows developed in other studies in the area. However, this study <br />was initiated because previous studies failed to account for significant input <br />discharges across 1-25 into the Cooper Slough basin from the Boxelder Basin. <br />Results of the hydrological analysis are in agreement with the Boxelder Creek LMMP <br />study (Reference 4). Comparison of the Cooper Slough basin to other basins of <br />similar drainage areas would be inappropriate dUB to thE! significant impact of the <br />Boxelder Creek basin ovmflows. However, field observations support the delineations <br />presented. <br />