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<br />Cross section information for Spring Creek was taken from topo- <br />graphic maps with a scale of 1:1200, and a contour interval of 2 <br />feet, flown on May l2, 1974 (Reference 7) and prepared for the City <br />of Fort Collins by Nelson, Healey, Patterson, and Quirk. Bridges <br />and culverts along Spring Creek were field measured. Cross sections <br />along Dry Creek were taken from topographic maps with a contour <br />interval of 7 feet. <br /> <br />Locations of selected cross sections used in the hydraulic analyses <br />are shown on the Flood Profiles (Exhibit 1). For stream segments <br />for which a floodway is computed (Section 4.2), selected cross <br />section locations are also shown on the Flood Boundary and Floodway <br />Map (Exhibit 2). <br /> <br />Roughness coefficients were estimated by field inspection. The <br />range of Manning's "n" used for this study is shown below: <br /> <br />Flooding Source <br /> <br />Channel <br /> <br />Overbank <br /> <br />Cache La Poudre River <br />Spring Creek <br />Dry Creek <br /> <br />0.035-0.045 <br />0.030-0.045 <br />0.030-0.050 <br /> <br />0.045-0.080 <br />0.035-0.060 <br />0.015-0.100 <br /> <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 />Starting water-surface elevations for Spring Creek and Dry Creek <br />were taken from the existing U.S. Army Corps of Engineers profiles <br />of the Cache La Poudre River at the confluences. Water-surface <br />profiles for Spring Creek and Dry Creek were computed using the U.S. <br />Army Corps of Engineers HEC-2 Water-Surface Profiles Computer <br />Program (Reference 9). <br /> <br />All elevations are referenced to the National Geodetic vertical <br />DAtum of 1929 (NGVD). Elevation reference marks used in the study <br />are shown on the maps. <br /> <br />8 <br />