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<br />MANUAL FOR ESTIMATING FLOOD CHARACTERISTICS <br /> <br />23 <br /> <br />SITES NEAR GAGED SITES ON THE SAME STREAM <br /> <br />. <br /> <br />Peak discharge information for study sites near gaged sites on the same <br />stream can be computed using the method described on page 4. The first step <br />is to determine the drainage area ratio of ungaged site to gaged site. If <br />that ratio 1 ies between 0.5 and 2.0, the equation given on page 4 should be <br />used to compute the required peak discharges. If the drainage area ratio <br />I ies outside the range, the method for "Ungaged Sites" should be used. <br /> <br />Flood depth information for study sites near gaged sites on the same <br />stream should be computed from the flood depth regression equations for the <br />region in which the study site 1 ies, The method is illustrated in Example 2, <br /> <br />Example 2.--FZood F~equency near a Gaged Site <br /> <br />Determine the QIO-, Qso-, QIOO-, and QSOo-year recurrence-interval <br />floods for Cherry Creek at State Route 83, il.5 mi south of Franktmvn, Colo. <br />(lat 39019'41", long 104044'02", NWi; sec. 25, T, 8 S" R, 66 W,). <br /> <br />Map coverage: Russel1vi11e Gulch quadrangle, scale = 1 :24,000 <br />Denver quadrangle, scale = 1:250,000. <br /> <br />From table 5, note that station 06712000 Cherry Creek near Franktown, <br />Colo. (AG =169 mi2), is located downstream. <br />age <br /> <br />Determine the contributing drainage an!a at the site (AU=132 miZ), <br /> <br />Check that AU is either more than half AG or less than twice AG: <br /> <br />AUfAG=132 mi2f169 mi2=0.78. <br /> <br />This meets the drainage-area requirement, and the fol1.owing relation is used: <br /> <br />x <br />QT(U)=(AUfAG) QT(G) <br /> <br />where x=0.48 for the Plains Region, and QT{G) is the weighted discharge from <br />table 5. <br />