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<br />
<br />
<br />locations On the White River Plat,'au andth~
<br />Park Range. This produced a 40-hou,.storm
<br />with a 3.35 inch rainfall o\.er the Yampa
<br />RiverdrainageaLo\'eAgnteCreekanda4.13
<br />inch llserage rainfall on the Park RanRe.
<br />l.u'\s rate" for the oasin weree~timateddue
<br />to lack ofreprodllcible rainfioods in the area.
<br />Swdy of runoff in theGrand:Mesaareadur.
<br />ing the 1970 Four Corners storm indicated
<br />high (grealer than 1.5 inches) initial losses. A
<br />study 01 strMmfiows and backup precipita-
<br />tion data in the U.S. Forest Service publi~B-
<br />tion entitled "Annual Streamflow Summaries
<br />Irom Four Subalpine Watersheds In
<br />
<br />Colorado.. (which include, West Walton
<br />Xorth Fish. and Soda Creeks) indicates th~t
<br />about z.o inches of rain must fall in the
<br />August to October period for appreciable
<br />runoff to OCCur. l.os8 rates adopted for the
<br />100- and 500.year general rainfloods were
<br />1.60 inehrs initial loss and 0.15 inch per hour
<br />constant loss on the '{ampa River. and 2,00
<br />inches initial loss ILnd 0.1l> constant loss on
<br />the tributary creeks. A lower ioitiallosswas
<br />used for the river basin because the density of
<br />vegctation is less th:1n in the basins of the
<br />tributary creeks, The .resulting flows are
<br />shown in Table 3.
<br />
<br />TABLE 3
<br />
<br />PEMFLOWS
<br />100_AND 500_ YEAR FLOODS
<br />
<br /> Peak Flow
<br /> ,',
<br />Stream locatlon 100-year 500-year
<br /> Flood' Ftood'
<br />YampaRiver Gaging Station (At Steamboat 8,000 20,000
<br /> Sprin!(>l)
<br />Soda Creek Corporate Limit 1.300 2.900
<br />ButcherknifeCr.,.'k Corporate Limit :I2() 1,300
<br />SpringCrcck Corporate Limit 650 2,400
<br />Fish Creek GagiogStation (Upper Station 1.800 4,600
<br /> near Steamboat Springs}
<br />Walton Creek Gaging Station (:\ear Steamboat 2.700 5,COO
<br /> Springs)
<br />Burgess Creek Near Storm Meadows Drive 360 10400
<br />
<br />'F....m'na\\'m.I'.u~mon"dby,.ia
<br />']-'Nm""ne,alra;nfo,tooYamp. Rivcr, r,om oIouJbu"t"",m, fo,' h. ',ibc"',y orc,"",
<br />
<br />As previously stated, there are little
<br />definitivcdatalLvailableondoudburstevents
<br />in the Steamboat Springs area. The June
<br />1921 fl<>Od may havt' been the result of a
<br />cloudburst that a\lgmf'ntpil lIhnorm.a1
<br />snowmelt runoff. Contributing rainfall
<br />totlllled 2.57 i",-,he&, but the peri<Xl 01 ~ime in
<br />
<br />whieh the rain fell is not definitely known, A
<br />newspaper aceount indicated that it might
<br />have been 1Z-20 hours. However. 2.0~ inches
<br />of rain in 3 hOllrs and 3.Z4 inehos 01 rain i" 24
<br />houn; ha\'r hppn re,ordro elswhprf' in the
<br />reglOn,
<br />
<br />8
<br />
<br /> TABLE 4
<br /> oaSTRUCTIVEIIRIOGrSANOCUlVEIlTS'
<br /> Ele..llon'
<br />I Unde,- 100_y..r 500-ye"
<br />IdcnllllenllM lo.otlon' Slr.omWd d.oro.",,' Roodwoy' Flood f<ooo
<br /> YAMPARIVER
<br />I S'oekDri\'O IS9.27 68,,6 lif,73 OOSO AA.'; ~f"'2
<br />13th.'\".",\ 189.73 6&78 lil;~;1 6';9~ ~, 6699
<br /> F""lbrirl~. 1!M1.0& ';"~~ ""iS7 r",,,, 61)~8 61Q2
<br /> 5thS",o: 190.31 6S9~ "'W ~71O 610~ 6108
<br /> D.&R.G,II',RR 190,70.... 610.1 6715 5118 &714 6717
<br /> D.&R.G.II' " In.zg- 67:16 6151 "" 0747 675..1
<br /> T>....II.",Hoad 192..~9 tn. 6751 "" 6749 615~
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<br />Cloudbur,;l$torm criteria were deHlopt'd
<br />from "Probable Maximum Thunderstorm
<br />Pr..cipitation E~timates for Southwest
<br />States," AUl(u'llDi2. A 40 ~rcentvalueol
<br />the probabie maximum precipitation p<>int
<br />rainfaH lor St<'amboat Springs. plotted at
<br />ILbout the 500-rl'nr fre-qupneyon as-hour
<br />rainfall (requcneyeuryC for Craig. Colorado
<br />(the near~st r<'Corded), was seleeterl as a stan-
<br />dlLrd project cloudburst storm. Loss ratcs
<br />
<br />OBSTRUCTIONS
<br />Natural obstructioos to floodflow include
<br />trees. brush, and other vegetation growing
<br />along stream" During- floods,vegetation im-
<br />pedes f100dflo\\" nnd results io backwater con-
<br />ditionsand increased fl<>Odheights. Brush or
<br />tr<!<!s washed out during floods and carried
<br />down"tream could coliect on bridge1; or plug
<br />,ulverl~, thus creating a damming elfeetand
<br />overbank flow. As floodflow increase.,
<br />mnsscs of debr;" ean destroy a briilge or
<br />cause watl'r le\'els to rise higher and more
<br />rapidly than normnl. thus eroding and
<br />
<br />adoptfd were identi,al to lh<>Of u,edfor
<br />general rainfall. The re,;lIltin~ floodflow5 are
<br />aiM shown in Table 3.
<br />InformationOl\ jU. and 50.,'ear Iklod cveots
<br />wa~ also developed in conjunction with the
<br />hydrologic studies madc fur this report.
<br />These are basiclLlIy snowmelt floods and. with
<br />theexceptionofshowin~ thcirwatersorflLce
<br />profiles on Plates 2.24. are not co,'ered in the
<br />report.
<br />
<br />damaging abutments. approache~. and the
<br />overlying roadbed.
<br />In generul. obstructions restrict f1oodflows
<br />and maycauseoverbanknows.unpr~ilictable
<br />areas of flooding, possible damage to or
<br />destruction of bridges and other stream
<br />crossings. and inereased velocity of flow im.
<br />mediately downstream. Most of the stream
<br />crossings in the study area (in Steamboat
<br />Springs)areobstrlldivetofloodflows.l'erti-
<br />nent data On these structurcs are shown in
<br />Tabie 4. The effed of obstructions may be
<br />seen on Plates 2-24.
<br />
<br />'(),I,,,,, ot.dO$i~"",<d by',
<br />',\lth. "I"tr.....m 11\0' 01 \h. ","clu,<. ,ouQ,j,'d loti1c' """"",:,,,t ,m<a"=,I,.:.ld~t"m
<br />'Ili,t,"o< from m.mh of "".m to "'idpoint or ,~r"et",.. (Yam!" Ri,'.r in m;lo:; Md o,~or ,t,.."" ,n [""',)
<br />'Al"".I',p.n,
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