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All of the Road System's drainage sub-basin areas were small enough <br /> in size so that aerial adjustments of point rainfall amounts were <br /> r� <br /> not required. <br /> Based on a general soil map received from the SCS office in Glenwood <br /> Springs, the soils are predominantly in Hydrologic Soil Group C. <br /> However, the upper portions of the North and South Forks of Dutch <br /> ff� Creek fall in Soil Group D which has a high runoff potential. The. <br /> t1 vegetation coverage type and distribution (forest, grass, barren <br /> ground, rocks, etc.) was estimated from the Colorado Office of State <br /> Planning and Colorado Geological Survey 7.5-minute aerial photoquad <br /> "Placita, Colorado." The soils groups, used in Figure S-3, Reference <br /> 4, determined the runoff curve number used in the SCS method. <br /> The precipitation value of 1.9 inches of total depth for the 10-year/ <br /> 1 , <br /> 24-hour storm was converted to runoff for each runoff curve number <br /> c <br /> using Table S-3, Reference 4. <br /> The time of concentration and travel times of surface runoff are <br /> important factors in determining peak flows. The time of concentra- <br /> tion values shown in Table 1 were estimated from a nomograph on <br /> t <br /> 1� Figure S-5 in "Peak Flows in Colorado" (4). This nomograph incor- <br /> porates what is generally known as the "California Method* which - <br /> is expressed by the equation: <br /> �J <br /> 1 . <br /> 39 <br />