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<br />FUTLiREFLOOO5
<br />
<br />L~rqer floods c~n occ...r in the tut...re th~n have occurred
<br />In the past in the study reach. To aetermine the flOOdinG ootential
<br />it "liS necessary to consider stor",s ~nd floods that have occurred In
<br />reo ions of like topoqraDl,y, waterShed cover, and physica I characteri~tics.
<br />Estimates of floodln'1 as oresented In this reDort are ba~od on the exlstino
<br />development of the watershed, Increased urbanization will alter rUMff
<br />conditions, and also result in chanqed flow conditions in the flOOd plains.
<br />Ols<:ussionolfuturetloodsinthisrenort Is IIl'1itedtotwofio+ential
<br />t loods, the I ntermad late R"qioM I Floo<l (IRfl, an<l the Stand~rd Project
<br />Flood (SPF).
<br />
<br />dlfticultto assign frequencies of occurrence with ~ny reasonabledeqree
<br />,. accuracy. Paakdlscharqes for the $tanddrd Project Flood ., selected
<br />locations 10 "'" stUdY reach ~ra a I <;0 shown '0 T"ble3.
<br />
<br />Table 3
<br />Potentilll Flood PeakDlsch"rqes
<br />Cache la Pbudre River at Greeley
<br />
<br />Loc"tion
<br />
<br />Dr"ina3eAreil
<br />SQ, lie
<br />
<br />Intermedl~te ReqioMI
<br />FIQodPe"kOlscMrqe
<br />c,+.s.
<br />
<br />Shndard Project
<br />Flood Deak Dlsch~rge
<br />c,f.s.
<br />
<br />Upstream
<br />25th Ave. bridqe
<br />
<br />1,890 9,400
<br />1,875 10,700
<br />1,825 8,100
<br />1,810 '1.61'10
<br />1,747 6,300
<br />1,723 9,000
<br />
<br />22,500
<br />
<br />At mouth
<br />
<br />INTERMEDIATE REGIONAL FLOOD
<br />
<br />Do"nstream
<br />Eaton Dr",,~
<br />
<br />25,000
<br />
<br />The Intermedl~te Re~ion~1 Fined Is definad as one thilt occurs
<br />"lth an IIvera~e frequency of occurrence of "Pout once In 100 years,
<br />althouQh It could occur in any year, ~uch a flOOd is a relatlvaly larne
<br />one ~M hilS been freQL",ntly used where a def inable tlno<1 I~ soLlnht te>
<br />outlineara"sin the flood plain f<'lrr",",ui2ltorvl>UrDO""Sand h".nl"COMe
<br />i1cceoted niltlonallv ". a usefui standArd for th~t nun'o<;.". The ne,,~ flows
<br />of this flOOd "'''10 J"v"lo~oo from ,;1,,1 1st k"i dn..I V"'t5 rJf sir",am fiaw
<br />
<br />Upstream
<br />Eaton Draw
<br />
<br />21,000
<br />
<br />Do"nstre.am
<br />25th Ave. brldqe
<br />
<br />29,000
<br />
<br />15,500
<br />
<br />recordsatFortColllnsandGreeleY,Calorado,u.inoroutin(ltechniauf.'s
<br />in conjunction wIth reqlonal analyseS to define flow~ at 5el~fed locations.
<br />PMk tlows thus doveloped for the Intermediate ~e"ie>nill Flood a+ solected
<br />loc2ltlnnsinthest\Jdyroachilresl>own in Table 3.
<br />
<br />lipslrad'niimit
<br />of Study Reach 26,400
<br />
<br />*EatonDrll"confluencewiththeC"chelaFt>udreRlver Islocatedaoout
<br />400 feet downstrellm from the Union P3citlc RaIlrOad hridqe.
<br />
<br />STAN)Af\O PQOJECT FLOOD
<br />
<br />Th~ ~t~n~~r~ P"~jArt ~Inn~ i~ ~Afin~~ ~~ ~ ~~!0r fl~rl ~~ir~
<br />
<br />can be exnocted to occur fro", a severe comb iM! ion 01 ,"cteoroloqical ,,~d
<br />hvdrolo'lical conditions th~t "re rea~oMblv chdrilctoristic of ne fjeofjra-
<br />phic~1 area i~ w~ic~ +hp s+udv i1rea i~ loc~ted, excludin~ e~trAm~ly r~re
<br />~vonh. Stor"'5 thilt would orodur:e tois f l00d ~re unCOl"1mon. a~J it i5
<br />
<br />2C
<br />
<br />"
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