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<br />POTENTIAL FLOODS <br /> <br />This section discusses th~ lntermedl_~t~ Reglon~1 ~nd the <br />Stand~rd Project floods ~nd their effects on the b~sln. The Int~r- <br />medl~te Reglon~1 Flood represents ~ flood .Ith an average trequency <br />of occurrence of ~bout once In one hundred ye~rs ~nd Is Incr~~slngly <br />being ~ccept~d by the public ~s ~ mlnlm~ st~nd~rd for ~ppllc~tlon of <br />local regul~tlons ~nd flood protection. Th~ Standard Project Flood <br />Is of g~ter magnitude and r~pr-esents ~ r~so~ble ,.pper limit of <br />axpectedfloodlng. HQwever, lllrger floodS;!!re possible. Itls <br />emph~slzed th;!!t floods which are smaller th;!!n the Intermedl;!!te Reglon;!!1 <br />Flood are muCh more likely to occur. Although these lesser floods <br />~Id Inund~te sm~ller ~re~s, they _~ld ~Iso c~use d~mage ~nd c~use <br />h~rdshlp ~nd Inconveniences. <br /> <br />Intel"ml.ldlllte Reglon~ I Flood <br />The dlsch~rge-frequency relationships for Boulder and <br />South Boulder Cr~oks wore devoloped from stre~m 9~gln9 records. The <br />rel~-tlonshlps wore computed by the Log-Pearson Type lei method <br />presentedlnBufle-tlnNo.15,December!967,"AUnlformTechnlquafor <br />Determining flood Flo., Frequencies", publhhed by the Wder ReSO<lrces <br />Council. Tho Intermedl~te Regional Flood for the two stre~ms both <br />~bove and below theIr confluence Is presented In table 7. <br /> <br />, <br />, <br />, <br />I <br />I <br />I <br /> <br />St~nd~rd Project Flood <br />WithIn I~rge areas such as the MIssouri RIver Basin, <br />floods oce~slon;!!lly occur whiCh ;!!re mUCh III~ger than the lntenmedl~te <br />Reglon~1 Flood. frequencies CMnoT be assigned with any reeson~ble <br />degree of IIccur~cy to these unus,,~1 floods, but they mus-t be considered <br />In each specific ~rea since they have been axperienced In the gener~1 <br />IIr~~. These unusual floods are r~presented by the St~nd~rd PrOjecT <br />Flood. AI-though unusu~l. these storms do happen liS Illustrated by the <br /> <br />" <br /> <br />1965 floods In th~ Danv~r area whlco r~sulted fro~ stor~s with inal- <br />v idua I cell s producl nJ ra i .,fa II of Standard Projoct Flood mugc itJJ~. <br />The 1<394 flOOd on 8o'Jid",r Vu"k prob"bly hed a rea~ di<;charge of ~bout <br />70 p~rcont of the ~tanCJrd Project Flood. It Is rass ilJle that thl s <br />storm produced Standard Proj<lct rei nfa II c~'1 Is ovor r>"rTS of th~ oas in. <br />T"bl" 7, bolow. sho'.s 0edk Jlsd>"rqu. for tho Standard Project Flood <br />eswcll as the I ntecmoJ liltc Req lana I Flood. <br /> <br />TA3LE7 <br />FLOODDISCiIA,1G::S <br /> <br />Location <br /> <br />Int"rmi1'dlato <br />Regional <br />"000 <br />(c.f.,;.) <br /> <br />Stilndar~ <br />Projoct <br />FlOOd <br />(c.I.,;.) <br /> <br />Boulder Crook above South <br />Boulder Crook Contluence <br />8ouldcrCreok belaw South <br />Bouldor Creok ConfluoncJ <br />South 8a~lder CrOOk <br /> <br />7,4Xl <br /> <br />15,800 <br /> <br />11,000. <br /> <br />21,0.00. <br />9,400. <br /> <br />5,0.0.0 <br /> <br />GCOilterFloods <br />floods even Idrgor tMrl the Stclndclrd Project floods arc <br />posslblo, hut -tho COMbInation of factors nocessary to produce such <br />f I <)(JGS 15 extrt'll\8Iy r~r". Such f le>ods ~"'" rx-t lurtrer d iscusse,j in <br />this report although they shauld not be ovorloake~ where it is <br />n"ceSSJry to ollmlnato all risk of flooding. <br /> <br />HalardsolGrudtFloods <br />Tho of feets 0 f t~e rospect i va I ntil c"",d j ilte I~eq i aMI and <br />StanC<lrdProjectFloodsworoanalyzedtodeterminethofloodpatontlaI <br />on both streiYnscovered Inthlsr<lport. TheanalyslswilsmadC'usinc <br />57 cross sections on 8oulJer:;;reekand 40 cross sGctionson South <br />BaulderCreek. The cross soctions W8ra surveyed in 196il. Tho"'ater <br /> <br />" <br />