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<br />. <br /> <br />. <br /> <br />, <br /> <br />" <br /> <br />.r <br /> <br />APPENDI X A <br /> <br />.. <br /> <br />UPPER RALSTON CREEK BASIN <br /> <br />The mountainous, forested basin above Ralston Reservoir is divided into <br />.subbasins 1,2.3.4,5,6. and 9, as depicted on the Basin Map- These subbasins <br />have their .headwaters near State Highway 119.- Elevations range from 10,000 <br />to 6,000 feet, and the terrain ranges from rolling grassy meadows surrounded <br />by,forest to extremely steep. rugged mountainous terrain. <br /> <br />The average ground slope varies from approximately 20 to 50 percent. The <br />creek itself begins as a 10\" point in the valley in the upper-most reaches, <br />and finally shows an identifiable channel near the lower end of subbasin 1. <br /> <br />Table 11-1 summarizes various physical parameters for each of the subbasins <br />in th~ upper Raiston Creek basin. Only present conditions were analyzed with <br />respect to runoff parameters here, since no significant development is <br />antipicated .for the upper basin. <br /> <br /> TABLE 11-1 <br /> UPPER BASIN PARAMETERS <br /> Overland Overland Streambed <br />Sub- Area Percen t Flow length Slope Slope <br />basin (Sq. Mi.) Impervious (F ee tl Percent Percent <br />1 6.4 10 1.200'" 20 7 <br />2 4.0 10 900 45 4 <br />3 17.0 10 700 40 5 <br />4 2.9 IS 1.200* 25 10 <br />5 1.5 15 1.200* 25 10 <br />6 8.6 15 1,000 50 7 <br />9 5.6 15 900 30 5 <br /> <br />*Maximum overland flow length used is 1.200 feet; defined channel genera~ly <br />occurs at greater lengths. <br /> <br />TABLE 111-) <br />100-YEAR PEAK FLOW SUMMARY <br />PRESENT CONOITIONS <br />(All values in cfs) <br />