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<br />Discharge-frequency values for the Animas River and Hermosa Creek in <br />the vicinity of Hermosa were taken directly from the U.S. Army Corps <br />of Engineers, Sacramento District, and based on streamflow records <br />of rain and snowmelt floods (Reference 6). <br /> <br />Peak discharge-drainage area relationships for Animas River, Hermosa <br />Creek, Junction Creek, Dry Gulch Creek, Lightner Creek, Los Pinos <br />River, Vallecito Creek, and Grimes Creek are shown in Table 1. <br /> <br />, <br /> <br />3.2 Hydraulic Analyses <br /> <br />" <br /> <br />Analyses of the hydraulic characteristics of streams in the county <br />were carried out to provide estimates of the elevations of floods of <br />the selected recurrence intervals along each stream studied in the <br />county. <br /> <br />Water-surface profiles of the selected recurrence intervals were <br />developed using the U.S. Army Corps of Engineers HEC-2 step-backwater <br />computer model (Reference 7). <br /> <br />Cross section data for streams in the area were obtained from aerial <br />photographs (Reference 8); the below-water sections were obtained by <br />field measurement. Cross section data for the Animas River and <br />Hermosa Creek near Hermosa were taken directly from the U.S. Army <br />Corps of Engineers Flood Hazard Information report (Reference 6). <br />All bridges and culverts were measured to obtain elevation data and <br />structural geometry. <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 (Manning's "n") were estimated by field <br />inspection at each cross section and checked for reasonableness <br />against a recognized standard text (Reference 9). The channel and <br />overbank values are shown below. <br /> <br />Manning's "nil <br /> <br />Stream <br /> <br />Channel <br /> <br />Overbank <br /> <br />! <br /> <br />Animas River <br />Hermosa Creek <br />Junction Creek <br />Dry Gulch Creek <br />Lightner Creek <br />Los Pinos River at Bayfield <br />Vallecito Creek <br />Grimes Creek <br /> <br />0,034-0.070 <br />0.035 <br />0.025-0.070 <br />0.024-0.040 <br />0.010-0.100 <br />0.035-0.045 <br />0.050 <br />0.050 <br /> <br />0.060-0.080 <br />0.060 <br />0.030-0.120 <br />0.050 <br />0,010-0.150 <br />0.060-0.070 <br />0.080 <br />0.080 <br /> <br />.. <br /> <br />9 <br />