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<br />L976 BIG THO~PSON RIVER FLOOD
<br />The BIg Tho~vson Rl.er hastn 1s adja~ent to and south of the Ca~he
<br />la l'oudre Riv..r b..~1n. Thb hhtodc fiood serves "S !In Indi~at!on of
<br />flood problems in the lllO<Jntain ar.". of the Cache L1 Poudr" River hlwin.
<br />
<br />ironically, there '"'as no r..in in the io,",..r end of the ~il.nyon. All the
<br />water came from <Jp~treaUl areas. This a~ded an "lo",ont of dlsbel1ef to
<br />waruings. At 9 p.~., the Loveland Police dispatcher reccived a ~ssil.g~
<br />ho", the State Patrol reque~ting a "arning from Dra<<e <.Io"'n the canyon.
<br />The dIspatcher follo~ed the Wave of water down the canyon by the teIe-
<br />vhon~ lInes that ~ent dead In the water's path as she ~a" calling to
<br />wsrnpeople. Wat"rswevtlxlulder., tree., vehicles, houses, "nd
<br />foundationsawayandleftther"ins.trewndo"natreall. Shortly after
<br />~il.rnings ~ere glven by the State Patrol, the flood passed through Drake
<br />and left dev8Stationanddeath 1n ttswake. ApproxImately 17.51l11les
<br />do~nstream from Eates Park, Cedar Gove was then engulfed and by 9:45
<br />v.m., the flood hit the area ~e8t of ~oveland. The flood~aters ran
<br />unchecked for nearly 5 hours. At 10:45 1""'., the ~ater and Po~er
<br />Resourc"s Service's 227,OOO-pound .iphon at the fW<Jth of the Sarro"s
<br />collapaed ~hen a flosting building hit the southern support.
<br />
<br />The flood On Dry Creek wl.shed .way or seriously d.11l1aged nearly
<br />"~erything in Us I'"th. .hree lives were loat. Dry Creek ero~"d n.'w
<br />and .dder ch..nnel~ in ""'ny places M.d caused con~id~rabi~ loss of land.
<br />
<br />At:nospherle conditions on H July 1976 cOOlbined to reed a heavy
<br />i"fto~ of "",1st aIr into the Front Range area of Colorado. This
<br />created unstable conditions unusually fa~orable for thunderstorms.
<br />
<br />Saturday, 31 July 1976, was the he ginning of a 3-day ~edtend to
<br />celebr"teGolorado'scentennial. In the 20-"lile long Big Tho:np'on
<br />Canyon, there '"'ere as ","~ny as 2,500 vIsItors and perlllanent reaidents of
<br />all age.. Bet~een 5:30 p.,... and 6 p.m., a light rain began in the
<br />F.8te~ Par<< area. in the upstrealll part of the canyon. An ""ploslve thun-
<br />Jeratorm develaped, ~ith thunderheads rangIng up to 62,000 feet stal-
<br />Itng in"tend of ""ving a~ross the are~ n~ t~ey "suatly do. Torrentl.~1
<br />rains estimated at up to 12 itH:hes In 4 h<>un fell In the p3rt af the
<br />,:>..b ~t'~ee... Estes !'o.~k :l"~ !)r~kc.
<br />
<br />WUhin 4 hours or 90, the worst of thE rdnfall ~as over and the
<br />peak no~ had reached the llIOuth of the canyon. In the Narro,",s "rea dt
<br />the mouth of th"- canyon, U b estimated that, .'It peak flo~, the velo-
<br />city of the ~ater ~"" on the order of 15 ",ilea per hour. Th"- frequency
<br />of the peak at the c.nyon tIlotlth has beenv3rlou.'lly eatil!lated at fro III
<br />300 yearn tn 750 v..ar.'. (4) At th~ ""',lth <It th.. Rig Thnmr.nn r"~y...~,
<br />
<br />Bet~een 6 p."'. and 8 P'''', travelers Wete encountering rain of
<br />incr~"slnll intenaity. The first "'...rnings of an l_inent dIsaster call1<'
<br />f,.orn telepho~e reports of torrentiat rains, rising "'ater, and ~asho"tn
<br />along \:.S. fl1ghway 34 by people who ~ere ~ger{enc1ng dHfieu1tles In
<br />the canyon. Early in the flood period, both en<.la of the highw~y e'cllpe
<br />route ~ere destroyed ..Ind 1t hecame .~ death trap for fr"ntic ""'torists.
<br />
<br />". flo~ Increa-qed frOIll ". norlll..'ll rate of 200c.f.s. " l.bout n,200
<br />e.[... Water lev..is " ". canyon reaehed fromlO " " feft "bove nor-
<br />=L (18) ", rainfall covcreda relativoly slllallarea. An <:>stiLUilted
<br />
<br />70squaretoileaofthetota1304.quaremlledralna.ge"reaat the
<br />canyon mouth contributed to the floo~ peak.
<br />
<br />At approximately 8: 25 p ''''', c" ll~. r<!pot t illg ; londing and ra~ues-
<br />t ing a id start ed t~e chai n of 'WOn~' wc. jt'O ""u l~ resu It 10 toe ",fort
<br />to ~srn people about th1;, O.."h fl"od.
<br />
<br />Ua~l.ge ~aa severe, not only be~ause of the great 'l~ of ~ater,
<br />but also because of debrh. Even '..hen flow dId not "ash a~~y a
<br />building, It was sever Ly dalI1.:l.ged by ~ londlng, by roc<<" sla=iug into
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