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<br />The mOre cOIl'iI1on flood In the C1!<::he I~ Poudre River study <br />reach I s that '~h IC1) exceeds rho channel capacity 01 about 5,1100 cub ic <br />feet per second bClt is Sr13 i lee than the I ntermedi ate R8<1 iona I F I cod . T~e <br />(lven'g'" annual reJk d i:Jc.~or'Je frCl'1 all records at tho Fort Coil ins <1ago Is <br />4,~38 cub ic fod P(,r 5<lcond, The Stdnd~rd Project Fiood is not the I~rqest <br />flood ~hat C"n occur in t~" study r"ad, ~ut the ~rotJ&>ility of lar,?,"r fl<l<'lds <br />becomBS increa,ingly rarote. <br /> <br />FUTLREFLOODS <br /> <br />T,,[)1,,4 <br /> <br />Two largo potentia I I loods '~ere devel<lred lor the study <br />reaCh inordertoassosstnefloodhalardt"ere, This"asdonebva <br />statistical analysis ot gaging records 1!nd the use o' routing techniques <br />for thB reacnosbetl/con tho gages. Oneflood,thBlntermediateRo<jional <br />Flood,or 10o-yeJrllood Is <jBnerally accented by the publica5a minimum <br />limit lor application of local regulations. Theother,theStar>dardProJect <br />Flood, isli:lrgerar>drepresentsareasonallleupper-Ilmlto!expoctedtloodin<1. <br /> <br />POTENTlA.tFLOOOPEA.KDISCfl;\.f1n;:S <br />CACIlE tA PO'J()tlE RIVE~ AT FORT COlli US <br /> <br />Lccatlon <br /> <br />Int~rmeJI~te R09lonal <br />Floo<lPe1lk <br />lisc~"rqe <br />-----c-.T:s-,~-__.h- <br />17,400 <br />16,200 <br />19,700 <br />19,700 <br /> <br />Upstre~m II",it 0' Studyl1each <br />ftbove mouth 0' Cc, Creek <br />'.leI"" MOuth 0' Dc, Creok <br /> <br />, <br />I <br />I <br /> <br />[lo,.,nstrea", I ;mlt of Stu~y Reach <br /> <br />Intormediatel1ej]lorll'l1 Flood <br /> <br />A d Ischarg9-froq~ency curve "as developed by a st"tlstical <br />anal ysis of stream! 101'1 records ~nd ;>~st floods In the study reach: thus <br />dofining the magnitude of the Intermediate Regional Flood. The Intermediate <br />Regional Flood Is delined 3S one that occurs once In 100 years on the average, <br />alt~gh It could occur in any year, The Intermedl~te Reqlonal Flood peak <br />d ischargos at sever" I key points I n the study reacM are s!la;n in t~b Ie 4, <br /> <br />Frequency <br /> <br />Standard Project Flood <br /> <br />The Standard Project flood results Irom a storm of ,uch <br />magnitudeth<it It isdifficulttoiissl<jna frequflrlcv to the recurrence. <br />It is defined more CO<n?letely In tho Dlossnry. The Denvnr ar~a floods <br />ot 1965 and thc 116pld City, South Dako~a f Ic:o<: of June 1972 ~re 'Jxamn Ie,; <br />of su<,:n ~ fl()('>(i, Tn" Sten<ii'trrl ProJ<>et Flmd pf'ak di5Ch~rges at several <br />point51nthestudyreacharesho.;nint.Jble4. <br /> <br />1{.1~~rd, 01 Large r loads <br /> <br />St~n~~rd rro.ied <br />Flood re~k <br />I'Jlschar'1e <br />-C-.T,-s-.~--.-_. <br />43,700 <br />40,000 <br />60,000 <br />60,000 <br /> <br />Hyd~au I Ie stud lo~ wcro "",de to dnt"rmi"e the t lood haldrd <br />presented by the I nter",edlate l'le'1 ion~ I and Star>dard Project Floods through <br />tho study reach. :honnol ond ovorb~'k cond Itions were represented t>y <br />bridge and va Iley cross ~ectlonz madB In 1972. "actors contrlbutln<j to the <br />tlood h.1Wrd include extent 01 oraa flooded, flood ~epths, oost.-uctlo"s to <br />flood 110.15, velocl1los of 11001 f 10. S, rate of ri,e of s~roarn leve I, and <br />duration of floocing. flood dat""Jagc~ ~€ncr3111' incre~se as f lood dept~~ <br />Ilnd voloc;tle5 i nCr<:!aSe, C1J~fructio"o, to I I ""0, tend to ceus<:' '~at"r lev,.15 <br />to riSB. <br /> <br />" <br /> <br />" <br />