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<br />-- <br /> <br />. <br /> <br />3.2 <br /> <br />ei <br /> <br />The SPF di~Charge of 219.000 cubic feet per second (cfs) at the <br />Pueblo gagEi! is approximately equivalent to the magnitude of the <br />350-year flood. Based on this, frequency curves for other locations <br />were devel~ped by assigning a recurrence interval of 350 years <br />to each SPF and constructing curves parallel to the frequency <br />curve at t~e Pueblo gage. These curves were extended to obtain <br />the 500-yefr dischqrges for Fountain Creek. From these frequency <br />curves, thr lO-, 50~, 100-, and 500-year flood discharges were <br />determined for use in this study. <br />I <br /> <br />A frequency analysis of the Pueblo gage based on a log-Pearson <br />Type III d~stribution (Reference 5) was made for this study using <br />flow recor~s of 1935, 1941 to 1965, and 1971 to 1977. In lieu <br />of the com~uted skew, a regional skew of 0.4 was used in computations <br />of peak di~charges and confidence limits. The U.S. Army Corps <br />of EngineelSfrequency curve falls within the 50-percent confidence <br />interval 0 this more recent study for recurrence intervals of <br />greater th n 30 years, while the 10-year flood is only slightly <br />larger tha~ the 0.25 limit. It was concluded that the U.S. Army <br />Corps of E gineers discharge for Fountain Creek at Manitou Springs <br />would be a opted for this study. <br /> <br />For Sutherland Creek, Williams Canyon, and Ruxton Creek, discharges <br />were determined using the regression equations described in Manual <br />For Estimaiing Flood Characteristics of Natural-Flow streams:in~ <br />Colorado (~eference 6). The equations for the Plains Region were <br />applied to I the portion of each drainage area below an elevation <br />of 9,000 f~et. Above an elevation of 9,000 feet, the equations <br />for the MoJntain Region were applied. It was found that the Plains <br />Region portion of each drainage yields much higher discharges <br />than the Mduntain Region portion. Consequently, the 10-, 50-, <br />100-, and $OO-year flood discharges from the respective plains <br />Region equ~tions were used. <br />I <br />Peak disch~rge-drainage area relationships for Fountain Creek, <br />Sutherland ICreek, Williams Canyon, and Ruxton Creek are shown <br />in Table l.! <br />I <br />I <br />The flood JisCharges for Beckers Lane Tributary and the upper <br />portion of Williams Canyon were interpolated from a drainage area- <br />discharge urve developed from computed discharges for Williams <br />Canyon and ISutherland Creek. <br />I <br /> <br />Hydraulic 4nalyses <br />I <br />I <br />Analyses 01 the hydraulic characteristics of the flooding sources <br />studied in the community were carried out to provide estimates <br />of the ele~ations of floods of the selected recurrence intervals <br />along each ~f these flooding sources. <br />I <br /> <br />9 <br />