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<br />. <br /> <br />Regional discharge versus drainage area curves were derived based <br /> <br /> <br />primarily on method no. 3. The final peak flow-area-frequency plot was <br /> <br /> <br />obtained from statistical analysis of three stream gages considered most <br /> <br /> <br />representative of the study area. (Reproduced in Figure-I) The stream <br /> <br /> <br />gage information was considered the most reliable source for flood <br /> <br /> <br />prediction. <br /> <br />III. DRAINAGE AREA <br /> <br />The drainage area of the South Arkansas River to the downstream limit <br /> <br /> <br />of the previous study is 196.5 square miles. The total drainage area to <br /> <br /> <br />the confluence with the Arkansas River is 210.4 square miles. Only 13.9 <br /> <br /> <br />square miles of additional drainage area is tributary along the study <br /> <br />reach. (See Figure-2). <br /> <br />The added drainage area is almost entirely located on the south side of <br /> <br /> <br />the river. Elevations range from 11,600 feet on Methodist Mountain to 6,900 <br /> <br />feet at the Arkansas River confluence. <br /> <br />Vegetation is Pinon and Juniper with sparse grass ground cover below <br /> <br /> <br />9,000 feet. Denser pine forest vegetation occurs at higher elevations. <br /> <br />IV. SOILS <br /> <br />A portion of the drainage area is included in the soil survey for Chaffee <br /> <br /> <br />County published by the S.C.S. The lower slopes below 8,000 feet to the <br /> <br /> <br />south of the river are included. Approximately 90% of the soils on these <br /> <br /> <br />slopes are cataloged as "Rough Broken Land" (Ru) or "Badlands" (Ba). Basic <br /> <br /> <br />engineering properties are not given due to the variability of the soils. <br /> <br /> <br />The hydrologic group also is not listed. Based on this sparse information, <br /> <br />-2- <br />