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<br />The more COffJ'lOn flood i[]theCache la f'oudre River study <br />reach i5 that -<1M iel' exceeds the _c'1annol c<l~,1cTty at ~bout ),(100 cub ie <br />fea~ !,cr second but I~ ""1aller ~han the Inter,:",dia~e Reqio~ai flood. T~e <br />av"r~80 ilnnUa I p""~ d i5chDr<)e f,-O'" D II records at tl10 "o:-t -:'";011 I 05 1aqo is <br />~,8YJ <:u~ic Ipet opr ';r"~",,d. Th" ,tMh,;",r~ Pro.;A"~ FlOOd is not ~he l"rQAst <br />"Iood -n",t c~~ occur in the ot~dV reac'C_. but ~'H'-oroodlilitv of 1"'-'l'Jr floods <br />I)ocomcs irlCre~sin~ly n...,<:rte. <br /> <br />FUTU'lEFLOO::;S <br /> <br />Til~ I c ~ <br /> <br />T~o large potential / loods ~ore develolJed I()r the studv <br />reach In o;dc; to assess the t I ood hazard ~he'-o. T~ i s wa ~ done b V a <br />stat i st iea I ana I Vs I 5 01 g~g i ng record ~ a rid the u5e of rout i rlg techn i QUOS <br />lor the re,lches betweGn the qilqe5. One / load, tho Intermed i~tc flo~io~a I <br />Flood, Or ID)-yoar f 100<1 is qeneril Ily ilecanted ~y the rub I Ic ilS a ",inlmum <br />I imit lor ilpp I ]catlon of loca I renu lations. The oth"r, t~" St"hJard rrQj,,<;t <br />F I oed , is larger nnd represemts a re"sonnb Ie unpar I le'l I ~ of cxpoctcd f I oed I n(l. <br /> <br />e>o:-ENTIAL FLGO) PEAK )ISCIIAf\CES <br />r.A~IE LA i'OLJ:JRE RIVEr< AT ForT COLLI~:S <br /> <br />LC:<:dtlon <br /> <br />l"t~rMAdinte Regional <br />FloodPeilK <br />_~~.1J.s.::.11.a.:iJ.()______ <br />c.t.s. <br />17,400 <br />16,200 <br />19,700 <br />19,700 <br /> <br />I nterm6diate Rogional Flood <br /> <br />Up"trn;,m lirnltotStudyn""ch <br />."!Jove r'lCuth of DrV Cr<WK <br />8dQ,ol O\Outhot DrVCreck <br />Do.;n5tre"",II",it-oIStucyReach <br /> <br />f, d IsCharge-lrequerlCy Curve was develop"d by a st~tlstTca I <br />an~ lysis 0/ streile'lf 10; records and pilst floods In t~e study reac~; thus <br />defining the magnItude 01 the Intermediate Reqlonal Flood. The Inter~&dlate <br />RogionalFlood isdctinedasonethatoccursollce In IIJGvearsontheaverilQe, <br />although It could occur Tn any year. The Intor~edlate Reqlonal Flood peak <br />discharges at several ~ey points in th~ study reach are shewn In t~blo 4. <br /> <br />Frequency <br /> <br />Stand,lrd Projed Flood <br /> <br />The Standard Project F loed resu I ts from ,~ storm of S'lCh <br />_':1agnitudetnatIt isditfi<;ult tOlJssigndfr",quencytotherecurro'),jCO. <br />I t is cot Ined "1Or(l complete IV in the Glrlssary. The Dt'nv,)r "r"", t lo"d~ <br />of 1').65 "lid tl", Rapid CIty, South Dakota flood of June 1972 are ()>(~"ml,,<. <br />otsuChatlood. TheS1"andilrd Project Flood reakdi!;ch1lrqesilt5evor,,1 <br />points In the s~u<!v reach are sl1CW n In tab Ie 4. <br /> <br />Ii,,~~rd~ 0/ Large Floods <br /> <br />St~r:d~rc "ro Ie<:t <br />F 100<.1 ro~~ <br />Oiscrilrqe <br />~-.-r.~~..~-_.- -- <br />43,7'10 <br />40,000 <br />60,00G <br />liO,OOO <br /> <br />IlvdrnJ I ic 5t,," ,,.'s w or~ modo to dot"rrr_ i~" too t I OO,~ r"'z"rd <br />pre5cptcd by tl.e Int('r~c~l:lto 1~"'!1lonal and St~nGard F't'"o:E'd "Ioa.j~ th~OUq" <br />t~,] stuc:y :-oact.,. Cro,ono I Clod overbank cond itio15 ~'er" re~r"sCtn+ed by <br />bri ,k]<' and va I I<,V cross soctlons mark ; n 1'l72. Factors ~"ntr;hLlti nq to the <br />flooa Mz~rd ixllJde exten~ 01 ""e~ tloo1ed. flood d""th~, oo5tn,~t;(.'f\5 to <br />t load t 1"",., vO loci tie~ of f IO<YJ 'fa" s, n,te cI risE' r;f strI')C"" lev>> I, nnd <br />dur"t ion 01 f 100<.1 i "'1. r lood dana'Je~ 'Jt:nera II y i rrcreaSe a'; f looe Mcrthr <br />and veloci ties In"reasB. CbstruC1 lor~ f'o '-Icws tond to C.'lU1r ~at',r lew'l, <br />torl1C. <br /> <br />'P <br /> <br />" <br />