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1 , 1 <br />ESTIM.STION OF 10, 50 AND 100 YEAR FLOOD DISCHARGES <br />• Estimates of peak flows from 10, 50 and 100 year precipitation <br />events were developed utilizing the techniques of McCain and <br />Jarrett (1976) as documented in the Colorado 4later Conservation <br />Board, Technical Manual No. 1 entitled "Manual for Estimating <br />Flood Characteristics of Natural-Flow Streams in Colorado". <br />Procedures followed were those designated for identifying <br />floods at ungaged sites in the mountain region. This technique <br />is also documented in "Procedures for Determining Peak Flows in <br />in Colorado;'SCS Tech. P.elease 55 as amended. The technique <br />utilizes a log - Pearson type III method for fitting a <br />frequency curve to gaging station data and multiple regression <br />techniques to transfer the results to ungaged sites. This does <br />not provide a detailed, engineering-design level study but we <br />• feel results of this approach are adequate for estimating <br />baseline hydrologic conditions. <br />The regression equasion developed by McCain and Jarrett for <br />developing flood estimates at ungaged sites is as follows: <br />bl b2 <br />yt=axl x.2 <br />where <br />yt = a flood characteristic, either peak discharge or peak <br />flood depth, for recurrence interval t; <br />xl,x~ = basin and climatic parameters; <br />a = regression constant; and <br />bl,b2 = regression coefficients. <br />• <br />