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<br />FLOOD DAMAGE PREVENTION
<br />
<br />Th",re are noexi>lingflood control projectS
<br />that have aneHect in the study area, The Dalla,
<br />Cree~ Project (Ridgway Reservoir) i, being
<br />cons1fuOed by the U.s. Watef and P<>wer
<br />ReSOUfce, Service at a ,ite neM Ridgway
<br />approximately 25 mile, upstream from
<br />Muntrose. The project will b" primarily lor
<br />water conscrvallOn and irrigation and is
<br />expected to he operational in 19a4,flood
<br />conaol will not bea function of the projecr and
<br />.e'ef>'oirrdeaseswillnotbecon1folledlmrhat
<br />p.rtiwl.rr..ason;therefore.rheeflectsofthe
<br />proj..cr were not con,ideredd."ingthis,wdy,
<br />However. future operation of th..re",rvoir for
<br />conservation and ,wrage ba,ed on ,nowmelt
<br />for"'c~sh could provide appreciable flood
<br />control benefih down<tream a, far a5 Montrose.
<br />Improvement5such a, dikes and bank prorC<'_
<br />rion hdV", been made at various localio'" along
<br />the river. Some incidental flood protection i,
<br />provided by ,eoe.al irrigation tanalstharbranch
<br />offfromlheriveratdifferentlocationsthrough_
<br />out the ,tudy area. However. no flood conrrol
<br />
<br />.weement> are in <>f(eer and tiwre ,ore no
<br />nireria fOfoper.ning the canals during flood
<br />periods. Concurrent with perioos ot snowmelt
<br />runofl. m..imum allowable flow-all gates
<br />open-I, u,ually in effett for the ir.igation
<br />c"nal'tome~' rhe...quirement,ofagticullural
<br />areas, DUfing period, of ("xce>li"ely hi~h flow,
<br />on the Uncompahgre River, trans-balin diver-
<br />,ions trom ,he Gunnison Ri,'ertn theL'ncom_
<br />pohgre V~lley .fe reduced '0 alleviale flood
<br />condition,. Flood control, howeve,. is not.
<br />normal ope'otion of the l)ncompahwe Project
<br />IGunni,onTLlnnpll.
<br />Montrose County and the communities of
<br />Montrose and Olalhe are eligible for flood
<br />insurance under the emergency phase of the
<br />National flooo In,uranceProgr.m. Rareltudie'
<br />nccell.ry ro convert the county and communi-
<br />tie, to the regula. program offload insuran('e
<br />are Icheduled /or the immediate luture, Data
<br />developed forrhl'studywill be.,'ailable for use
<br />by the federal Emergency Managemenr
<br />Agency,
<br />
<br />.nn""II-",ak Ilow, Vo'''U' 'ypP or ~o,'nt ,h<,w,
<br />liw followinK r"l..ti'H"hip h,.t'H''.'n ,no\"'mplr
<br />
<br />and rain annu,1 p"'" II",,,, JI lh" Ddt. and
<br />Colon, ,1feorl1 ~.)~..',.,
<br />
<br />Gage Slr..am \'..a" 01 ~ll'~ of henVNumber o!~~':'.tJdl P".!<-.l!(':",s
<br />Number- G~g.. Il..,ord Sno..melt Rolin
<br /> ---
<br />, Ddr" ~ '" 21
<br />, Colona .. C,l' "
<br />"
<br />
<br />,~, ,"Ow" 00 rh' "0''''''; "-"r.
<br />'C,,"N,I t." ,"~meo'NI 'oe ,"",,,I f"'" tk", ,i, t;,),,~
<br />>Goo,',,1 'OJ, ,u~",e,,,ed "" ,",,,,I ,,,.,. limy;",. 'il""\
<br />
<br />The,efore, to d'''ermine flow, oftll(' loo"year
<br />"nd otht'rfrc'quency flood,for this repon.
<br />"nnual peak flow5 for rain and ,nowmelt 10;
<br />r("corded by rl", Oeh" and Colon. ga~e,)were
<br />analyzt'dind"pend"ntIY,<lntlfrequencycurve,
<br />dpvel"ped for each, AII-C'vent p,'ak flow_
<br />frequency curv..s ",'rt' drvel"p"" hy,ombin_
<br />
<br />ing the r"iol.1I and snowmdt Ilow_frequency
<br />cu.oe,lorcachgoging't.rion, Itw." found rh.,
<br />the all-event curve, were ellemi.lly idemi,>al
<br />for the two 'toti""" Th"refore.unlform pNk
<br />Ilow, lor all bur a few location, In tlw 'tudv
<br />reach wer.. adopted, Peak flow v.llue, thu',
<br />determined are shown in T.ble2.
<br />
<br />TAIllE2
<br />PfAK flOW VAlUfS
<br />LJncompahgr.. Ri....r. Mont.os.. Sludy Ruch
<br />
<br />Flood
<br />hequ..nty
<br />10-Year
<br />50-Yeaf
<br />100-Ye..
<br />SOO_Ye.r
<br />
<br />FUTURE FLOODS
<br />
<br />100- AND 500- YEAR FLOODS
<br />
<br />Although flood, with magnilude, and fre_
<br />'1uencie"imil" toth",,'rh.llhav~o<xu"Nlin
<br />thepa"muld ""'U(,r1i"""i"n "ff"'u".floo<J,
<br />in thi, 'el""t ,doh" prin,>ip"l!y to thosp
<br />de,i~noted ." 100- "nd 500-,..'" flood" A 100_
<br />ycar Ilood h.... pe..k 1101'.' m.l~nitud" wirh" 1
<br />p",,'cnt "h.,1l'c "f being: ,,~u.lII,.d or ("x(epded
<br />in any giY<,n,.ear,or a frequeney of OCCtHren",'
<br />of "lmllT onr~ in 100 V1'M' on th.. long: "'rm
<br />.ver"~".Similarly.'tI,,,5oo-yearfloodhasJW'Jk
<br />tlow magnitu.-J,' Wilh a 0.2 percent chon,:" at
<br />b,'inS.'q\J.llled or eX('",-d",l in any lli"en year,
<br />orJ frequency 01 on:uflenC'e nf.lb,,,,l On,.. in
<br />'il~t ,"',,,, <>n th., I(}n~ '"rm a''''"~('. Tl mvst b,'
<br />und""'lOod thar rhe le'm "100.",,", flood"
<br />
<br />relale,to lIood maK"ilud,' "nd doe, not m"an
<br />that lhe lIood will O<Tur one time in a lOO-YNr
<br />1""lod. .""ntially. "probability 01 o,cu"~nc~"
<br />isimpli..". Thm,duringrhe lerm"i;",.v~r;oW'
<br />mu,tgageI30y"."I,lhechanceofalOO-yeM
<br />Ilood o('urrin~ i, ;'ppfo,i",al,'ly 1 in 4; durin\<(
<br />.,,,av,'r"Sl'lifctime 170 yea"l,the chan,'e of..,
<br />f()().veorfloodi,apprmim"tdylin2.lnJl00_
<br />v~,'" perio.-/, ,h~ d'M",e of J l00-yC'Of flood i,
<br />J~~r,,'in\Jtell' 3 in 5,
<br />Srudi,,, m"Jp for thi, r~port ,huw th.l
<br />Iloodllows on ,helin""mp.hgrc RivN ",ually
<br />,,',ult fr"n"n"wmell. but m.o>' "I,ore,ui,from
<br />K"",.r.ll ..in, p,,,r;n,I.,,I,. alon~ th" lowe,
<br />,,',,(h,', ",Ithp ri..'r An ",,,Iy,,,,,fhi"o"c-;ll
<br />
<br />At the dioe"io", ,(runure, for EJ>! C,,,"I.
<br />Iromlone Com"l. "n" '-'1')f1lfo'e "nd Delta
<br />Canal, only tho", flow, rh~t 1'<1" lhrough thc'
<br />"""rure, durin~ periods of peak flo.. in th,.
<br />main channel W..f.. rlPtNmined hoe<$ Ill;,in
<br />ch""nel flow would flood 'urroundin~ land,
<br />Jnd th.." rcturn TO th,' mai" chon",'1 dow,,_
<br />
<br />OBSTRUCTIONS
<br />
<br />1><.'ur.,1 ",b""wtinn, '0 tl""dflow ;ndud,'
<br />trec" b.OIh. .nd nth.., v,'g"IJlion ~")\'iln~
<br />.lonK ,t".,,,,,,, IJlJ_in~ f1oo<k w~.'tJ1'on
<br />
<br />Flow
<br />(cis)
<br />3,100
<br />'.<00
<br />,<>00
<br />6,600
<br />
<br />"'eam Iw"'th..div""iom.
<br />Peak flowvaiue, lor the llh 50-, 100-, and
<br />'i(J(l_yeM floods, together with the ,>orresl'""d.
<br />ing w.te' ,uffoc" ele';lti"", fst.ge'I,;or "o,:h
<br />""" '~c'tio" u,.,d in th.. hyrJ.."li,. .,naly'"
<br />nwl,. r"r rhi,"'port.." ,hown inAppcndi,,>\..
<br />
<br />iml','d,', ilo<,dtlow and ""ul" in b,,,'kw,,t(.'t
<br />"",d;rion,an<l;"..",.",,1 flood hell/"I<. Hf",h
<br />or Ifpe,wd<lwd ".n du",,~ ilood, JMI "."ied
<br />
<br />"\.',;.~h ul ,,,,,,,,I n"',, ''''', wo,.,"" ,0<1 ,"'0"'''''''''1, ("',, '" e,,,," ",.".,,,", ,,,.' ""'1"'"''''
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