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<br />rain durIng 2 and
<br />~hlch 4.18 Inches
<br />
<br />~ A.ugust;
<br />fellon2
<br />
<br />Waferdale measured 4.64 inches, of
<br />
<br />FUTURE FLOODS
<br />
<br />talning about 1,000 acre-Ieet
<br />on 3 August. The flood crest reached Loveland at 11:30 p.m. and
<br />the peak thoro was estimated to be 22,000 c.l.s. The river ~aS
<br />reported to be a mi Ie wIde I n places. Numerous rura I homes ~ere
<br />fIOOded,rTI(Inysweptlromthelrloundations.OnemlleofU.S.
<br />Highway 34 west of Loveland was washed "way. I rrlgation ~orks,
<br />such as dTversion dams and canals, were destroyed, crop loss ~as
<br />heavy, and there was much sediment and erosion damage. The lives
<br />of four people were lost and many were left hc>:neTess. Total dam-
<br />ages from the llood were estimated at 1602,000.
<br />
<br />August. On Buckhorn Creek, a dam con.
<br />of stored water, faiied at 10 p.m.
<br />
<br />Floods 0/ the same or larger magnItude than those that
<br />have~curredcouldoccur In the future. To determine the flood
<br />potential of the study area, the 10-year, 50-year, 100-yellr, and
<br />SOO-year fiOOds wero analyzed. The results 01 thIs analysis are
<br />presented In thIs report as a means 01 demonstrating the elfects
<br />of large floods.
<br />
<br />JulY 1976. Heavyrainfall,omountingtoasmuchas
<br />12 inchos in <I hours, lell on the evening of 31 July in the ~P?er
<br />Big Thompson River b~5ln Tn the general vicinIty of Estes Park,
<br />GienHi'lven,andOrake. Thelntenserainl(lll produced largeilmounts
<br />01 runoff on trIbutaries at the 319 Thomp~on River as well (lS on
<br />theBigThompsonRlveritscll. Flash flood conditions prevlIlled
<br />lrom th.. rllinfa II area downstream to the mouth of till, Ellg Thomp~on
<br />Ri ver cMyon ~est of Loveiand. The csti"a~ed roo, discharge at th..
<br />U.S.r;.S. stream gagIng statIon located on the Big ThompSQnHiver
<br />6 miles east of Drake was 31,200 c.f.s. - about 4 times larger than
<br />the prav lous racordod pc"k discharge. (lan\,Jges Irom th [s I load ~cro
<br />e~ti"atod lit about $35,000,000 In Larim",r Coullty and ~bout $45,000
<br />In Weld County. One hundred thirty-nine bodies were recovered in
<br />the flood aftormath with ,ix p"rwns listed as ,tiil missTng.
<br />
<br />Discharge magnitudes for floods analyzed In this report
<br />~are based upon an analysis of stream gagIng data at the U.S.C.S.
<br />stream gages located nei'lr Drake and LaSalle. Informationonthese
<br />stream gages wa~ presented in table 2. Because there are no stredm-
<br />flow gag[ng rocords between the LoSallegageand the upstream
<br />limit 01 the study, discharge-probability relationshIps were devel-
<br />oped lor tho intervening drainage are~ using unit hydrographs and
<br />I load routing tochnlques and rainfall probabillties/remU,S.
<br />Weather Burllau Technical Publication No. 40. The lollowlng table
<br />presents dischilrge data used In this report.
<br />
<br />TabieS
<br />Summary of Pertlnont DISCharges
<br />lor the Big Thompson River Ba~ln
<br />
<br />Location
<br />
<br />O""i(l<jge
<br />Area
<br />(sq. mi.)
<br />
<br />IO-Year
<br />Dlsch"rg"
<br />Peak
<br />(c.f.s.)
<br />
<br />50-Year
<br />Discharge
<br />Peak
<br />(c.f.s.)
<br />
<br />100-Year
<br />Discharge
<br />Peak
<br />(c.l.s.l
<br />
<br />SOO~Year
<br />Oischarge
<br />Peak
<br />(C. t.~.)
<br />
<br />L"rimer-~'old
<br />CountyL1ne
<br />Llpstre"m Irom
<br />Little Thompson
<br />River
<br />Oo~nstrea'" from
<br />Llttl<;Thompson
<br />River
<br />
<br />,,,
<br />
<br />3,600
<br />
<br />7,600
<br />
<br />10,000
<br />
<br />18,500
<br />
<br />'"
<br />
<br />2,200
<br />
<br />4,700
<br />
<br />6,500
<br />
<br />12.000
<br />
<br />'"
<br />
<br />3,200
<br />
<br />7,300
<br />
<br />9,900
<br />
<br />20,000
<br />
<br />"
<br />
<br />ConfluencewTth
<br />South Platte River 819
<br />
<br />2,500
<br />"
<br />
<br />5,90U
<br />
<br />8,000
<br />
<br />15,000
<br />
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