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<br />n:TERMEDIATEREGlOrMLFLOOO <br /> <br />FPJTIJP.fFLOODS <br /> <br />The I ~te""'edl~te I'egio~~ I Flood I s one that cou I d occur about OtcO <br />it. I 00 VOJr~ on the ilvoragc, J I nou~h I t may occur; n Jty year. Thl ~ <br />flOOd was dete~.lned by the use o' flcw-freQuency curves derived <br />fnom streamflow reoords. Consideration was ~Iven to characterlstTc <br />climatic conditions as they relate tosllOwmelt, and +0 runoff <br />characteristics of the basTn, takTng Into aCCdunt transmountaln a~d <br />Irrigation diversions, and the effect of Incidental storage provided <br />by upstream oo~servaTlon reservoirs. Flows on the GunnTson River <br />were further mod;fled to reflect flood control operations 01 Pacn!a <br />and Slue Mssa Reservoirs, MOdification of floodflows on the Gun~Tson <br />River substantially reduces peak flows In the ColoradO River down- <br />stream from the mouth of the GunnIson RTver. <br /> <br />Althouoh Iloods of the sane ~~1nltude as most 01 those that h~ve <br />occurred In the past could recur In the future, discussion In this <br />report Is Ilrnlted to those deslqnated as the I ntetmed late Reqlcnal <br />;ond St;Jndard Project Floods. TheSt;Jndard Project Flood,a rare <br />event, wou Id be I arqer and would occur less I re(1uentl v than ~n <br />Inter~edlate Reolonsl Flood, but could re~sonably be e~pected to <br />occur In the future. The most severe flood conditions on the ColoradO <br /><>ndGunnlsoni,lversare likely to occur durlnn tnosnow"",lt runoll <br />season/rornlateApril through June. <br /> <br />Th(1 1 lood I n}l to be e~pacted frQl'l drainage b~sin5 tributary to <br />the Colorado and Gunnison Rivers in the stUdy area are nnt inclUded <br />In this report bocduse I!IOSt drn Iflss thin 2-; SOUdre milos ir. ilrei) <br />"nd;os $UC~ ~r" C(>n<;id",rpQ 1-n ~,., '''r~1 drClin,,,'" rr"blPn"s. ()I h~ <br />throo I argor era i nuqos. I nd; an ',;a5I', wh ICh has been a f lood threa~ <br />to !jrana J u'lction, ; S no," co~trclled bv ,~ Sol I Conservation Serv ice <br />proj..'cl that atfcr1s protectl"n ;JweinS1- runotf 01 St"ndarq ~m,j"ct <br />Flood ma<Jnltuuc. <br /> <br />The peak flows derived for the Intermediate Regional Flood on <br />tl1eColoradoRlvtlr above and Mlowthe mouth of theGunnlsonRlvor <br />andonthBGunnlsonRlv6rbelowRedlend50",""reshownlnTabloZ. <br />Stage hVdrooraphs of flow$ In the Colorado ;Jnd Gunnison Rivers, typical <br />0+ tnOSG to be aXp.lcTed for an Intermediate Reolonal Flood In the <br />s~udV ~ro~ are show~ On PI~te ~. <br /> <br />STANOAROPROJF.CTFLrlOO <br /> <br />[)e~rj:;. collecti n9 on ~r I dge piers ,,"0 ~aDO'J; t ion of si I t In tMo <br />channel arc no~ ox~octed to ZJWSC reductTon in channel capacity or <br />cau>,;e ~n increaso ;n ~"t"r depths (b,xk",~t"r eflectl upstr.,,,,,, of Ihase <br />sfructures. 0" Iy tilt! .,ff"ct of veqet~Tjon normellv ",xl sl I ng j r. th", <br />1 ICXlo,..ays ~ere cOns I doro~ In prep"ri nq tile m~DS, prof; le~, dnd other <br />i IIu5trJtlon5 SIl(lWing the I ntern\edi "te """I ona I "nd St~ndarc Froject <br />FI=ds. <br /> <br />StMdJrd Prcject FlooJ runoff Is th"t q:meratea by the "'-'st severe <br />combination of metaorol~lcal cnnMltlons reason~bly ch;Jraeterlstlc 01 <br />the hydrolo~ Ie region, excl ud 1"11 extremely rare combinations. Peak <br />flows +or Ill" Standard Project Flood on t~e Colorado and Gunnison Rivers <br />wero develnped In the s~~ manner ~s descrlbe~ for the Intermediate <br />Regional Flood. Peak + lows for sel ected 10catTons on the two rlv<lr~ <br />,~re show~ I n T~b I e 2. <br /> <br />" <br /> <br />" <br />