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<br />MANUAL FOR ESTIMATING FLOOD CHARACTERISTICS
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<br />27
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<br />Example 4,--Uountain Region
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<br />Flood information is required for Geneva Creek at U.S, Highway 285 cross-
<br />ing (lat 39027'35", long 105039'47", NEi;NEi; sec. 9,1. 75., R. 74',1.).
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<br />Map coverage: Mount Logan quadrangle, scale = 1 :24,000
<br />Denver quadrangle, scale = 1 :250,000.
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<br />Parameters
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<br />Q=discharge, in cubic feet per second,
<br />A=drainage area, in square miles,
<br />P=mean annual precipitation, in inches, and
<br />O=depth, in feet.
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<br />A=77.1 mi2,
<br />p=28 inches (From U,S. Weather Bureau (1967) isohyetal map. Use grid
<br />method to obtain P at 20 points in basin and average,),
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<br />Q10 =O.12AO.81Spl.S92=O,12(77.1)0.81S(28)J .S92=O,12(34,51) (201,31)= 834 ft3/5
<br />Qso =0.91Ao.79Spl.llO=0.91(77.1)0.795(28)1.110=O,91(31,64)( 40.40)=1,160 ft3/s
<br />Qloo=1.88AO. 787pO.932=1.88(77,l)O. 787(28)0.932=1.88(30,56) ( 22.32)=1,280 ft3/s
<br />Qsoo=8.70AO.766pO.S60=8.70(77,1)0.766(28)0.S60=8,70(27,90) ( 6.50)=1,580 ft3/s
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<br />010 =0.44AO.196pO.347=0.44(77,l)0.196(28)0.347=0.44(2.34)(3.18)=3,3 ft
<br />050 =1.05AO.192pO.133=1.05(77.1)0.192(28)0.133=1 ,05(2,30)(1.56)=3,8 ft
<br />0100=1.44AO.187pO.OS9=1.44(77.1) 0.187(28)0,059=1,44(2.25) (1,22)=4.0 ft
<br />0500=I,94AO.184=1.94(77.l)O.184=1.94(2.22)=4.3 ft
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<br />If desired, use a graphical solution for Q100 and 0100:
<br />Ql00--Refer to figure 5.
<br />For A=77,1 mi2 and p=28 inches,
<br />From figure 5, Qloo=1,280 ft3/s,
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<br />D100--Refer to figure 6,
<br />For A=77.1 mi2 and p=28 inches,
<br />From figure 6, D100=4,O ft,
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