Laserfiche WebLink
2.04.7(2) <br />relationships estimated from a regional frequency analysis of <br />• gaging stations in the Gunnison River Basin. Records used in this <br />analysis covered at least 10 years of unregulated flow. <br />A regulated peak flow frequency curve for present conditions <br />at the Somerset index point was developed from analysis of flows <br />recorded after construction of Paonia Dam, and from reservoir <br />routing studies previously made by the Corps of Engineers and the <br />Water and Power Resources Service. Regulated peak flow curves <br />for the downstream index points were developed by: <br />1. computing the difference from the curves developed <br />for natural (unregulated) and present (regulated) <br />conditions at Somerset, and <br />2. subtracting that difference from the curves developed <br />for natural conditions at the four downstream index <br />points. <br />• Peak flows (for the 10-,50-,100-, and 500-year floods, existing <br />stream regimen) resulting from the foregoing hydrologic analysis <br />are shown on Table 2.04.7(2)(b)(i)-3. <br />Peak flow values for 10-,50-, 100, and 500- year floods (together <br />with corresponding water surface elevations) at each cross section <br />used in the hydraulic analysis made for this report are shown on <br />Table 2.04.7(2)(b)(i)-4. <br />Profiles of the 10-, 50-, 100-, and 500-year floods near Somerset <br />are shown on Drawing 2.04.7(2)(b)(i)-2. Flood elevations were <br />computed through use of the Corps of Engineers step-backwater <br />program HEC-2. Basic cross section input was from field survey <br />data furnished by the Colorado Water Conservation Board and <br />Delta and Gunnison Counties. Depth of water in the channel <br />and adjacent flooded areas can be determined from the profiles. <br />• <br />Velocity of flow during a 100-year flood on the Plorth Fork <br />Gunnison River would average about 7-10 feet per second in the <br />5-53 <br />REVISED May 15, 1981 <br />