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<br />I 76-1(35) PE <br /> <br />The Manual recommends that these predictions should be weighted with <br />stream gage data. The weighting equation is: <br />Qw = QgN + QpE <br />N + E <br /> <br />where: Qw = weighted peak flow <br />Qg = log pearson III of gage <br />N = Number years of gage record <br />Qp = predicted peak flow by Manual <br />E = equivalent years of record <br /> <br />Using E = 10 years as recommended in the Manual, we get: <br />At Golden using 6-7195 Q100(w) = 7570 x 77 .yr. + 11 ,300 x 10 = 8000 cfs <br /> 77+10 <br /> 6060 x 48 yr. + 26,400 x 10 <br />At Mouth using 6-7200 QlOO(w) = 48+10 = 9750 cfs <br /> <br />Some USGS personnel feel that the Manual deserves more than 10 years <br />equivalent record. They suggest as much as 50 years. This gives: <br /> <br />7570 x 77 yr. + 11,300 x 50 = <br />77+50 <br /> <br />9000 cfs <br /> <br />At Golden using 6-7195 Q100(w) = <br /> <br />At Mouth using 6-7200 Q100(w) <br /> <br />6060 x 48 yr. +26,400 x 50 = 16,400 cfs <br />= 48+50 <br /> <br />These discharges are plotted on Figure No.5. <br /> <br />Studies by Others - In 1964 the U. S. Corps of Engineers4 published a <br />predicted Q100 = 7300 cfs for the flow above the Ralston Creek confluence <br />and 8000 cfs below the confluence. However, in their letter of <br />August 14, 1975 to Mr. Brasher, District 6 Engineer, the U. S. Corps of <br />Engineers suggested that the Q100 at the mouth would be in the range of <br />15,000 cfs to 25,000 cfs. (See Appendix). This preliminary range was <br />estimated using the E.P.A.'s Storm Water Management Model (S.W.M.M.). <br /> <br />4 U. S. Army Corps of Engineers, "Flood Plain Infonnation", Volume III <br />Technical ~dix Bear and Clear Creeks, .(January 1966), p. C-4. <br /> <br />8 <br />