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<br />FL.OOD HISTORY
<br />
<br />The Colorado River ha, a lonjl: hi"tory of
<br />~n()wmelt n()odinjl:. but, due w tbe rural
<br />natureo[ the region. detail~d information on
<br />flood e,','nts in the ~tudy area i, not available
<br />The fint flo,w.1 of r~eord 00. the Colorado Riv~,.
<br />in tbestudyar<"aocc\lrr<"d in./un\'-,july 1884.
<br />
<br />FL.OOD DAMAGE PREVENTION
<br />
<br />Th,'r.' al"" M fl<...; "',ntrn! pr"j"e(,; Ihat
<br />ha",-,aneffeetintilestud;:an'a.R"<erv,,irs in
<br />the Colorado HiHr Basin abo,'e the study area
<br />are operated [or water con~ervation purposes
<br />arldeon'5~querltIYP"ovideonlyineidentalfl(>Od
<br />protection to the P"lisade area. However.
<br />in~identai <torage, trans-mountain diversion.
<br />and irrigation use~ hav~ served and will
<br />probably COntinlle to ~erve in reducinv peak
<br />flowsofv"rylarjl;eflood~ in the atudy re,wh.
<br />Fiood plain regullltionshaveb<,en adoptfd
<br />bj' ;,.re~a County. Desil<nat"d flood plains.
<br />induding!"w hll,ard lInd fl""dw(\y ".<ln€8. are
<br />incorporated inw county zomnv maps.
<br />AIJPlieation,fornewd~velopnLem()fr(,visinn
<br />ofexi,tinjl;devdopmentinthm;eare,,<nm<tbe
<br />"llprowd by tile County Cnmmis<ion, and
<br />
<br />OBSTRUCTIVE STREAM CROSSINGS
<br /> El<lvallon'
<br /> Und<lr_ Topol 100-year 500_y..ar
<br />locallon' Streambed clearance' ~oad"'ay' Flood FloOd
<br />~3.06 41;05 4625 16:JO .1,,::H l()29
<br />100.:';;; 4677 11,96 4701 ,1';~8 nlH)
<br />402.81 1fi91 nt" 1721 4721 4723
<br />
<br />Otner floods on the river wert' r..wr,IKJ in
<br />1917. t~20, t921. 19:;.\ 19,,2,lInd 1%7. Tb,'
<br />1:384 flood i, !l:enerally con"ider~d tbe most
<br />s,','''re knnwn en the Pali~ad,' area.!t resulted
<br />from rapid mdting of a d"l'P ,"owpack and
<br />eoncun'ent hp,wy rain,.
<br />
<br />fhJdflows for the COIOl'"do River at Palisade
<br />wern det€rmined [rom the reKi<l1\al pnvelope
<br />curves. Peak flows thus det,'rmined were
<br />68.000 llnd 82.1H:tO euhi~ fL,<,t pcr <eeond.
<br />rpspcetively,forthe100-andSOO'yearfloods
<br />at the upstr~Jm limit of the study area.
<br />
<br />sueh new"r r.'v;s,'dd~wlopmrnt;<s"hj,'rtli\
<br />pro"i,i<lnsdesi~nedtoprohibit:
<br />a. Storal<~ o[ materials that are floatabl~
<br />"rm"y bed"wimental to human. animal,or
<br />plantlik
<br />b. DisDO,al of !ladJa!<~ or other solid
<br />wag\<' material,.
<br />t_ t"'sid<,ntiallls~_
<br />d. Crcation or deposition of additional
<br />debris.
<br />e, Pl"cementoffill.in,tallationofstruc.
<br />turt.s, or ,l"rag" of materials that tould
<br />adve,-,;elyaUect rloodflow and pos,ibly cau,e
<br />additional f1c>oding.
<br />Palisaui!hasamningl'l'dinane,".iJutitur>eo
<br />Ilntaddn'," fh<d haz~nl<.
<br />
<br />OBSTRUCTIONS
<br />
<br />~atural obstructions to floodflow include
<br />tree,. brush and other vegetation growin~
<br />alonl< streams. During floods. vei(etat;on
<br />impcdt'S f1""dflow and resull' in backwater
<br />condition, and iner~aoed flood height.~. Brush
<br />or tree, washed out during floods and carried
<br />rlowMtream eQuld collect on bridges or other
<br />obtruction'.tbu,creati"gad:J.mmin~dfcct
<br />ami overhank now. Ag rJoodrJow inCrell'leS.
<br />maSilelQfd~briscandestn>yabridgeoreaU;lt
<br />water lm'els Ul rise hil':herand mOre rapidly
<br />than normal. thus eroding and damal<in"
<br />abtltrnents. apllroache,.an<! theoVC'rlyin!<
<br />
<br />FUTURE FLOODS
<br />
<br />100- AND SOO-YEAR FLOODS
<br />
<br />Th..l{lO-y,'ar rIco"l i'''n~withapeakflow
<br />magnitude tbat llas a I pere,'nt eil"""e of
<br />oci"~eq"all,'dor",,,,,,.~hjinanYf!,"iH'nyear.
<br />and a frequeoey ofoccurrcn"€of"b--,utonc,, in
<br />100 YPar. on thplon!l:-tprm "verag". Similarly.
<br />the ;>O(J-y('u flood ha~ a u.2 p,'rc~nt eh"n,,~ "r
<br />bein~ c'<lualletl 01" ,'xe..~led in alLY jl,'i",'n yoar.
<br />and:J. fretiu,'ncy ofocetlrr~nccof"hilUton"C:n
<br />.300 y~ar' on the lonjl;,u>rm ,,,'c,',,,,,,,. ,\,
<br />previously imikatfd, "M\I'mclt runoff fro'"
<br />U". Colon"lo Kiv..,' drr.in"jI,'p ha~ln ('r"Htr' th~
<br />
<br />Identlflcation
<br />
<br />Hl()~t ,..".'re floodcon<lition, in the study area_
<br />H"ltional JOO- and ;;OO.yr:,r )wak flow
<br />vall,," wpr" dctermin,~l from rliscbarge
<br />frequcncy data compiled for r<.>prc,cnti\tiH'
<br />stream v,a"inl\" station, in ,'"rlier Colorado
<br />River Ba,in ~tudil'S. The p,~~k flow "alu~s
<br />w"reconverted tndiscbal've in cubic f"..t p<,r
<br />second. per !'.quare mile (CS.\l). and envelnp<,
<br />"urvc,<,w<','c d",'do1Wd showing \(l(l-:l.ndG()().
<br />yc.U "nownw!t !lOCI! e"nn.s G" ,; ,c.:inn,,1
<br />h"<I.< Th<' \111)- a"d .)l~.I'Y""e ,~{)wm<'lt
<br />
<br />:lZRo",d
<br />U_S. Highw(t.;' 6-::4
<br />1.70 TOIrnoffto
<br />l'ali,ade
<br />
<br />l~formalionon lll-:<nd 5tl.rear flood ,"'cnl,
<br />wa, al",> dcveloped a~ part of the hydrolol1:'ic
<br />,tudie'conductedforthisreport.Tlw"",would
<br />also h>: snowmelt flO<Kls, but with thcc~cep'
<br />tionof,~huwinl<tbeirwatersurfaeeprorik;on
<br />Plate,27.81,:.rcnoteoveredintbcrepon.
<br />
<br />roadbed.
<br />In ~enen,LobstrLletion~ rt'Striet f100dflow,
<br />and may eausc o,'erbank flow,. unprediet~ble
<br />area~ of floodinl<. possible dam".'(e to or
<br />de~truetion of bri.-Jll:t's and otlwr stream
<br />um;sinp;s, and intrcmlCd velocil.\' of flow
<br />immediately downstre"m_ Two river
<br />",,",sinKS in Uw ,tudy ar~a arc ou,tructive to
<br />flo<ldflow8. Pertim'ntd"ta on the>;(' RtroctUfes
<br />arc shown in the following: tabul:<tion. Th,'
<br />effect ofobstrudions mal' be s~en on Plates
<br />27. 30, and 31.
<br />
<br />.\l tho u!-"i,,"," L."."i lb. "trucwro (Oxc.'r' f",,,'f"" ".,dwa)). "'" n<1",1 ",tn"",,,,,,,,!,,,,. """'" ,,',:,'wl ,ht<.,.,.
<br />'~;I",ul"tr"ar" r"m, IA'"", F.",,_,.. '>";,..n..
<br />" IM"t<",1,tl'lw,,",t[l<';nto".tn,"'",,,,
<br />'M'.h, "."~., Ii'~'n("",j ,,,,m,',ll.,,I,. "1m_ ,,,"1""1..,,,,,"., I";"'.
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