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<br />B18
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<br />FLOODS OF 196,') IX THE UNITED STATES
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<br />SOUTH PLATTE RIVER BASIX, COLOHADO, .rl.TXE 1965
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<br />B19
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<br />(TOSS sections f..urye.yed :1fter the Hood were near 15 fps (feet per sec-
<br />ond), which implies maximum velocities of about 20 to :2:2 fps.
<br />The amount of scour and fill, the size of the cottonwood trees that
<br />were uprooted or bent o\"er, and the matted condition of the debris on
<br />trees are physical indications thn.t confirm the computed \#elocities.
<br />The ;~D,DOO cis lw,lk Oil. Cht'rry Creek nenr ~lel\"in o(:('urred at 18:.W
<br />hOllrs on .Tune ]() and \'-as Q.:3 times the prc,"iol1s maximum dischaq:re
<br />in it record extending ]Javk to In:w. It. t.~\'(>n excceded the peak dis-
<br />ehal'ge of 34,000 ers, at :t site G m.iles do\Yn~trean), (':H13ed by th\: f:.\il-
<br />ure or Castlc::\yood D;Ull in l!i:):). The .June 1Do;":; Hood "'as the rpsult
<br />of a to G inches of rain in a few hours o\.er most of the drainage below
<br />Frankto'\vll. The peak flow at. the gaging station abo\-e Frunh.iown
<br />'..Y-n.s only 1,000 cfs and occul'recll1/~ hours after the peak passeu llIeh-in,
<br />about 18 miles downstream.
<br />Inflow to Cherry Creek Rosen-oil' from Piney ('reek readwd a rate
<br />of 14,100 crs at 1500 hours on lJune 16. The entire flow into Cherry
<br />('reek Resen.oir was stored. Based on a cha.nge in storage of Rto acre-
<br />f('ct in the 10 minntl's lJet\\"(>{>]) 10:20 and HtW honrs on June 16, the
<br />lwak inflow rate ""as ;)!)~OO/J ds. The increase in contents during the
<br />2,1, h01.11"':5 ending at l7DO hours all .June 17 was 1-!,770 'acre-feet.
<br />The ungaged area between :MeIvin and Cherry Creek Dam is 27
<br />square miles. If the combined flow of Cherry Creek and Piney Creek
<br />'\yrrs "t5,000 cis nt abUilt 1900 hom"s un June 16, the ungaged area wouid
<br />have to contribute H,OOO ds to obtain the computed peak inflow rate
<br />of 59,000 ds. A flow of 14,000 ds from 27 square miles is compatible
<br />with the location of the ungaged area with respect to the rainfall.
<br />
<br />SOUTH PLATTE RIVER-PLUM CREEK TO BIJOU CREEK
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<br />The contribution to the flood area of the South Platte River basin
<br />above Plum Creek was rel:tti,-ely small. The flow at the iYaterton
<br />gaging station was only 1.100 ("fs at the time the flood ("rest from Plum
<br />Creek entered the South Platte Hi,-er (fig, 6).
<br />The flood crest on Plnm Creek tra,'eled the 15 miles from Louders
<br />to Littleton on the Sonth Platte Ri,'er in 21h hours, and channel stor-
<br />age and other losses reduced the discharge from 1:>+,000 ds to 110,000
<br />ds. (A flm,- of 110,000 ds for 2'; hours would supply the entire Dem'er
<br />iVater Department demand for "SO days, or 19 months, at the a,'erage
<br />use of 122A5mgd (million gallons per day).) The flood crest took 4%
<br />hours after passing Littleton to reach the gaging station at Deu\'er,
<br />11 miles downstream, where the attenuated peak discharge WaS ';0,300
<br />ds.
<br />The pen.k flow 011 Sand Creek was 18,DOO cis and reached the South
<br />Platte Ri\"p.l' <1.bo1Jt 4 hours before the mai.."1 crest. Peak discharges in
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