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<br />
<br />The Gunni.on River i. tributary to the
<br />Colorado River. joining that stream at Gr.rld
<br />)urlction. The uncompahgre Ri,-er ;oin~ the
<br />Gunniwn from the south nu' D"lla. 80lh
<br />~tle.ml rile at high elevationl on the western
<br />slopes of the Continental Divide. Elevations in
<br />Ihc drainage area range from abO<.I1 14.000le"t
<br />lNGVD) in headwater regioOltO 5000 leet at
<br />Della, The upperorainageareasarecharacle,.
<br />iz"d by l1igh mountain p"ah. Sl<~ep.walled
<br />canyon~, and narrow valley., while broad
<br />expansel of lowhHisa"d melascharact"rize the
<br />lower region.. Stream gradienll along Ihe
<br />reache~SIl.ldiedaverage about 10 feet per mile
<br />on IheGunrlilon Riv"r arid 30 leel pc, mile on
<br />the Urlcompahg'" Ri"er.
<br />
<br />NATURE Of FLOOD PROBLEMS
<br />
<br />Climilt.. of Ihe GUrlnison-Ul\Compahgre
<br />Rivers regiorl i. arid to ,emiarid wilh rlormal
<br />annual pledpilaliorl varying from about 6
<br />indle. irl the Delta arN 10 40 inches in
<br />hNdwalerareas, MOI\of the anrlual p,ecipita-
<br />tion irl the high eleNtioOl of I"C Gunnison
<br />balin occurs a, \flOW and a deep Inowpack
<br />usually accumulates. Although seneral rain
<br />over IMse areas for eJ<tended periods can occur
<br />from July through Octobe', and corwective.
<br />typ.. c10udburll storms O"U' from late May
<br />\hrougnSeptembcr,runofl fromtne~type.of
<br />~lormdoelnotConstitUlease'ioulfloodtn'eat,
<br />Therelore, rapid s"",,'melt (rom about the
<br />middle of May th,ough early July po,,,, the
<br />mostlerioulf!oodhaza,dalongthestl.ldyreach
<br />01 tfle-Gunnison River. Snowmelt flood condi-
<br />tionlmaybeintl'nsili"dbygerle,alraindUflng
<br />lhelnowme1tINIOrl.
<br />Thc a,'crage elevation of the Uncompahglc
<br />Ri,."r basin is lower than tha\oftheGunni~on
<br />Riverba'irlanddeepsnowpacknormallycove..
<br />a proportion~l!y sm~ller part of the d,ainage
<br />,,'ea. Conv<,lIely. rain .tonTII OV.., Ih.. Uncom-
<br />pahg,e bas;rI cover ploportiorla\iy large, area~
<br />Ihan in the Gunnison ba~in. Floodi"'galong the
<br />IOWN Uncompahgre River l.lsually re\llhl from
<br />rapid snowmelt from mid.May through early
<br />July.butmayalm,e,,,hfrornrunoffofgl'ne,al
<br />rain,part,cuiilriy in the Delta a,ea.Onlhelong.
<br />tcrmaveragc,rainfloodso<;curle.,hequenlly
<br />lhan"'o.....lIlcltf\O\XJ,.whid,"'",u"irll"".ifleJ
<br />
<br />-----
<br />
<br />In th.e hi~h el.....ations of the tribulary a,,,as,
<br />vegelatLon lfIc1udes stands of pine and fi,.
<br />lnglem~n spruce. a'pen, and dwarf juniper.
<br />Cottonwood. sagebrush. other low br",h and
<br />sh,ubs,andwmenativegras~espredominatein
<br />Ihe lower .rea.. The Gunni'>OrI River drainl
<br />about7,OSOsquare miies (includi"'g Roubideau
<br />Creek) above Ihe lower Iimitofthesludyarca
<br />and 5,271 square miles above the Highway 92
<br />cro..ing rlear Austin, whiCh is about 6 miles
<br />downstream flom the mouth of Ihe North fOlk.
<br />The Uncompahg,e River drain. about 721
<br />square miles above 01athe .nd 1,129 ,quare
<br />miles at its moutn. A general map of Ihe study
<br />area and it,lributary drainage is shown on Ihe
<br />oppolitepagc.
<br />
<br />by ge",,,r.1 rain. Snowmelt rUrloH al1enuaH"1
<br />along the lower Uncompahgre Rive, due to
<br />ch.nnel Itorase and rlumerous diversions for
<br />irrigatiorl.
<br />
<br />Although high flows oil the Gunnison and
<br />Uncompahgre RivNsa,e large\yconlained in.
<br />channel and overbank t10wis infrequent,the.e
<br />Slfeam. have a long hisloty of damaging flood..
<br />Prior 10 INtlemenlof the area, Cnipcta, wile of
<br />the Ute IrldianChiefOur.y,ltated she had seen
<br />the Uncompahgre Valley at Della "flooded
<br />from bluff \0 bluff." The la..;;e't known liood on
<br />the Gunni.on River occurred in June 1684. 1\
<br />re,LJltcd from rapid snowmelt and was intem;-
<br />lied by heavy rairl. Since the ",owpack waS
<br />espccialiy de<'p Ihat year, ~nd covered large
<br />~reJlinwcstcmColorado,itisprob.blethata
<br />ll'e.t f\ood aho occurred on Ihe Uncompahgre
<br />River. InMay 18ll-4,thatweam wal reporled to
<br />be rapidly rising a"d expected to overflow-
<br />Re<;:ords show that, lince.19OO, hiSh flows
<br />o<;cufledon the-Gunnison and Uncompahgre
<br />Rl,erl in 1921,1927,1938.1941,1944,1947,1957,
<br />1'l7J,and1975,Highflnwsal.ooCCLJrredonthe
<br />GunnllOn River in 1905,1920,1'169. and 1970.
<br />Peak flow. of thclargelhistO'ic~ltloodsonlhe
<br />GUnllison and Uncompahgre R;vct.in the study
<br />a'N arc shown in the tabulation on pag..4.
<br />Hi,torkaUy. lioo-ch on the GUrlnison and
<br />Uncompahgre Rive" have di",-,pted highway
<br />auo.! rail traUic and darnag~-d or destroyed
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