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<br />MANUAL FOR ESTIMATING FLOOD CHARACTERISTICS <br /> <br />21 <br /> <br />GAGED S !TES <br /> <br />. <br />i <br />i <br />, <br /> <br />Peak discharge information for gaged sites can be obtained from <br />tab 1 es 5-8. The recommended va I ues for use are the we;i ghted-average d i s- <br />charges listed on the second 1 ine for each gaging statIon. The procedure <br />used for computing the weighted-average discharges is described on page 3. <br />The flood depths for the 100-year flood based on observed gaging-station <br />data are listed in the last column of tables 5-8, This method is illus- <br />trated in Example 1. <br /> <br />Examp 1 e 1. --Flood Frequency at a Gaged Site <br /> <br />Determine the best estimate of QIO-, Qso-, QIOO-, and Qsoo-year recur- <br />rence-interval floods for station 06712000, Cherry Creek near Franktown, Colo. <br />(lat 39021'21", long 104045'46", NE~ sec. 15, T, 8 S., R. 66 W.). <br /> <br />Map coverage: Castle Rock North quadrangle, scale = 1 :24,000 <br />Denver quadrangle, scale = 1 :250,ODO. <br /> <br />Determine the Plains regression flood discharges QT(R) at the station. <br />Basin parameters required are A and SB' <br /> <br />A=169 mi2 and SB=32 ft/mi, from table 5, <br /> <br />QIO(R) =144AO.S28SBo,336=144(169)o.S28(32)O.336=144(15.01) (3,20)= 6,920 ft3/s <br /> <br />Qso (R) =891AO.482SB 0 ,IS4=891 (169) 0 .482(32) 0 .154=891 (11.85) (1.71 )=18,050 ft3 Is <br /> <br />QIOO =1,770AO.463S 0.086=1,770(169)0.463(32)0.086 <br />(R) B =1,770(10.75)(1.35)=25,690 ft3/s <br /> <br />QSOO(R)=5,770AO.432=5,770(169)O.432_S,770(9,17)=52,910 ft3/s <br />