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I I I I I I I I I I I I I I I I I I I I IV-7 e; vi' .. - ..( ).j ., -' r ft ~, ut'(l~ 1,f'-1IQ{lJ ,,--~ Where Qg = st'at.,istics for Fraser River at Granby -{x '. -/ Qw = stahstics for Fraser Ri ver at Winter Park " Qs = statistics for St. Louis Creek near Fraser Qv = statistics for Vasquez Creek near Winter Park Qr = statist'ics for Ranch Creek near Fraser Om statistics for Meadow Creek Tabernash " = near The associated multiple correlation coefficient R is 0.987, the coefficient of determination R2 is 0.975 and the standard deviation is estimated at 107 cfs. This means 97.5 percent of the variation in Granby flood is ex- plained by the variation in the tributaries and th~.t:he Granby flood can be L7,,.-'!:'(i ~ 6' predicted within 3 percent of accuracy from adding tributary basin floods. The average deviation of the estimated IOO-year flood is within ~ 107 cfs. Table IV-3 tabulates IOO-year flood peaks estimated from the four different methods. The recommended peak is 3,300 cfs which is the result of the regression analysis. The frequency-discharge curve for Fraser River at Granby is shown on Figure IV-3 and frequency curves of each of the five sub- drainage areas used in the regression equation development are attached in the Appendix as Exhibit (1). TABLE IV-3 ESTIMATED IOO-YEAR RETURN PERIOD FLOOD FOR FRASER RIVER AT GRANbY Method Used 100- Ye ar Fre- quency Flood (cfs) 2,900 Remarks Technical Manual No.1 Colorado Water Con- servation Board Mean ann. precip. = 22" Area = 285 square miles U.S.G.S. Water Supply Paper 1683 3,780 Mean elevation - 9,720 Frequency Analysis 3,550/3,050 3,300 W.R.C. Guideline 1977/1981 Multiple Regression Analysis (1) Recommended value (2) Used data from Worrall & Sato's Study result