|
<br />""II., 'lnci by a depo~i~ of sediment inside. E~osion caused ~on"ide~-
<br />able dam"B" to U.S. High"ay 34. Tho "'>c"t damage oceu~~ed 0" the
<br />out'id"ofs"",l1-radiuscurves. Autornobllespllrkedonroad$ections
<br />~hat ""re st raight or elev.~red above the fluod of l.", escap"d daM!?e,
<br />howcve~, as th" road w~s not "ash<cd away.O)
<br />
<br />T~e frontal-ty~e stO'", oc~ur" \oIhen a cold air ",,,ss moveS into the
<br />region fro" the north 'It the sa"'e time tha~ "oist al,. is tr"n~p()rt~d
<br />tnto the region by a low pr"~"U,e sy" te'" s()u~h of the '"gion. The
<br />Mist ai~ i6 l(fted along ~he cold fr"nt an,] ~urved "estward "nder ~he
<br />i~fl"encc of the 10" p,ess~,e cell to the south. Pre~ipitation beco~e.
<br />general behind che cold front.
<br />
<br />The effect of the flash flood was :olni"",l heyond Loveland.
<br />')amages \oIere esti""'ted at over S3S,OOO,000, lDost nfwhich"ere to
<br />hlghwaysorprivatebulldings. A county survey indtcated that 252
<br />str~ct~re8 "ere da=ged more than 50 percent.
<br />
<br />Cloudbursts, due to daily te"'perature variatIon., occ~r durIng the
<br />sUmmer in the mountaln regions and over che plains area "lthl~ abo~t 7S
<br />lDiles of the foothills. The mornIng sun resulcs tn greater heating
<br />OVer the ",ountains than over the plalns. A flo", of air ~p the nlountaln
<br />slOpe" soon originates. Thunderhead. form over the lDountalns. The
<br />thunderstorms, which begin about noon in the mountains, move in a
<br />northeastward direction and are d{ssi~ated over the plains. The
<br />intensities of the thunder~torma are influenced by Che volulDe of !Doist
<br />
<br />Xany reports state that there \oIas an approximate 4S-mLnute warning
<br />to residents; other repon. .tate that sOme people received no "a,ning.
<br />The tragedy lies in the fsct that many warntnga "e,e noC heeded. Xany
<br />people de~ided to remain in "hat seemed to be a secure .ituation rathe,
<br />than venture Out ina dark, roadng storm, or they dedded to stay
<br />~here they were because they sa" no rain. A total of 139 hodies "ere
<br />recov~red and 0 have been declared ~is5tng.
<br />
<br />unstable air lnthe reglon.
<br />
<br />FLOOD CHARACTERISTICS
<br />
<br />Most flood~ along the Cache la poudre River have been ca"sed by
<br />rainfall adding to snowmel~ in the month of June. It is poulbla,
<br />ho;;ever, for se~e'e flooding tu occur fro\ll ,a1nhll aloIle -- as
<br />avideoced by the disastro~a 51g ,hom~aon Rtve, flood.
<br />
<br />;;y:mO:':':GIC Cll.!J,...C7!:RISTICG
<br />
<br />Sto'''' Types. Threeileoe'al type. of storffi>loccll,inthl. region.
<br />~ost severe storms usually o~cur during the spring and '''1lIIIler with ~ay
<br />"ndJunehovingthegre3teatfre'luencyofcccurreoce. gightypercent
<br />ur more of the annual preci?1t~tlon fall, during the Bro..tng sea.on
<br />fron:'farchthroughSeptember.
<br />
<br />DiSCharge-Probability Relationships. The discharge, of floods at
<br />selected probabilitie. are listed in table 6. The 100- aod .jOO-year
<br />flood diSCharges at selected locntion. ~re di.played on plate 2.
<br />
<br />'fos t of the ""jOI storms h~ve bee" caused by a pros sure synCT:\
<br />.'I,tc~ involv~s a high pfp.8sure are~ tel t\w north of th" regicm and"
<br />bw prL'ssure H~a to chc south. ,\," ""sCllc, a "",ist ~ir "".1"" fro", th~
<br />(,n If n' 'I<,xi cO t~ c"r;l~d '.est".rd ~LrOS" t'.~ h.l..ln ""j j"t,). t"\O
<br />ea"t<.'ard face ot the Front :l"ng"s. Ileavy pr<.,~ lpttdt I"~"~ re,ult" over
<br />th~ ""ount-ling fro", t~'e "".,ist ..i, b~ing lirl,'d Ui' th~ UlO'_'ht~l<l slol'''~'
<br />
<br />The ~ydr<)logtc ~cuJics used co dcri~"- the di.ch"rges are p,ese~ted
<br />ln voluOle n. 01sch~"~e' in the "",untains "er~ det"rlllL<led by us~ of
<br />the Xas,achusett. r<lstitute of ~echnology C~tch~e~t (M1TC~"L) 'fodel.
<br />DisellOrge. 1n the p~,'ins \oIere det<,'",ln"d ~y "ynthet1c ",,-it hydro~raphs.
<br />,rom th~ flood history and fro", t~ble fi ~(ld plHe 2, che ~n"n""ti"n of
<br />;>e"k dls,.har",e. a. ElOOdwdt"''" l~~,'~ the Jlollnt..,ins .,nJ cross the pbi""
<br />i. ~,'hl<'nc. h t~i~ dnal)"ot", att~nuatt"n r~"ult, fr"", v~ll~y .t,,,,'g~.
<br />
<br />"
<br />
<br />2~
<br />
|