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<br />correlation with published information. The roughness value for the main channel of the <br />Big Thompson River was 0.035. Roughness values for the overbanks were 0.050. A <br />roughness value of 0.020 was utilized where gravel pits were present. <br /> <br />Cross sections for Buckhorn Creek and Redstone Creek were taken from topographic maps <br />at a scale of 1 :2,400, with a contour interval of 2 feet (Reference 23). Bridges were <br />measured to determine size and structural geometry. Roughness coefficients were <br />estimated by field inspection. The channel value for both streams was 0.035, and the <br />overbank values ranged from 0.045 to 0.100. Water-surface elevations were computed <br />using the USACE HEC-2 computer program (Reference 22). <br /> <br />For Coal Creek water-surface profiles for the return frequencies were determined using the <br />U.S. Army Corps of Engineers HEC-2 computer program (Reference 22). Roughness <br />coefficients (Manning's "n" values) were determined from field inspections and ranged <br />from 0.040 to 0.070 in the channel and from 0.050 to 0.070 in the overbanks. <br /> <br />23 <br />