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<br />eludes ,iynificant infiltr~tion of precipitation, and enco~rdyes
<br />moisture to runoff quickly).
<br />
<br />Oitches
<br />
<br />~'ithin the upper, non-urbd~ized ~ortion t~e :;tudy re~ch, char.nel sec~
<br />t ions ~re typically of significant capacity with I(;(lderate to hedvy
<br />overbank yrowth. The plant ~rowth ~ 1 on~ the b~nks can cont. ri bute to
<br />debri,generation. TheArroyoflO>lsthroughthecity in o channel
<br />whose numerous crossings are only marginally adequate for tile fi veyear
<br />f requency stor~l r~noff. !~ojor ~urt ions of t.he ci ty are, therefore,
<br />susceptible to potentially severe flooding at relatively frequent
<br />i nterv~ 1 s.
<br />
<br />Several irri gation ditches cross the study basins, not~bly the
<br />South Canal (fed by the Gunnison Tunnel frOln tloeGunnison Ri..er), and
<br />the LOlltsenhi zer Cana 1 (which dr~ws fruII' the iJflcolf'pahgre Ri ver). The
<br />South Canol typically carries '?lJO-1000 cfs cfflow, while tile
<br />Loutsenhizerconveysapproxirnately200cfs. Other irrigation ditches
<br />in the basin include the Vernal Mesa Ditch, Hie Hairpin Ditch, the
<br />Garrett Ditch, the N-1 Lateral and the r,B Lateral. These ditches carry
<br />sign1ficantly less \'later than either the South Canal or the
<br />LoutsenhizerCanal {i.e., 50cfs orles,),
<br />
<br />Reservoirs
<br />
<br />Tnestudy redchofOryCedarCreek liesbet\'leen its confluence
<br />with thetJncompah<,;re River and afJproxilllately the intersedion of
<br />Ki nik in Hci~hts Road and Pahgre Road. ~'ithin the study area, the reach
<br />is typified by channels of si~nificant cafJacity with ~enerally heavy
<br />overbank gro\'lthwhich frequently extends into the main cliannel con-
<br />veyancearea. 1',oclldebris is generated in the upper redches of the
<br />watershed, cOlllposedprimarily of dried sagebrush and other vegetation.
<br />Th i s debri s, ,Ihen washed downstrearn and accu~lul ated, has the abi 1 ity to
<br />obstruct the strea",crossings, resulting in a reduction of capacity.
<br />
<br />There are numerous reservoirswithinthc study basins. Twomajor
<br />reservOlrsilydraulicallyisolatesub-basinsM-22andM.23 (see Figure
<br />11-3) from the remainder of the basins. The reservoir isolating sub-
<br />basin M-22 is Fairview Reservoir, the municipal reservoir. The name of
<br />the reservoir isolating sub-basin M-23 is unknown. This reservoir ",as
<br />recently enlarged. For the 100~year event, the water surfaces of these
<br />two reservoirswouldrisefrom2"toless than l',whichwould be con-
<br />t~i ned within the normal operati ng freeboard.
<br />Montrose Reservoir (CerroSumit Reservoir) is located at the
<br />extreme upper end of Cedar Creek, at Cerro Su~it.
<br />
<br />Table 11.3 indicate, the study reach lengths of the three study
<br />stream,. Figure VI-2 sho\,s typical photographs of tlie study strea,"s.
<br />
<br />TABLE 11-3
<br />STUDY REACH CHARACTERISTICS
<br />
<br />There is asrnall on-streamirrigatfonreservoirlocatedapprox.
<br />i Ina 1. e 1 y 1200 feet downs t redr~ of t he Ogden Roa d c ro ss i n g of ~-1on t rose
<br />Arroyo. The c~pacity of this reservoi r is estiuldted to bt' 2.5 acre.
<br />feet.
<br />
<br /> Study Reach Average Reach
<br />Stream Len~th Channel Slope
<br />Cedar Creek 11.6 cliles O.70i:
<br />Montrose Arroyc S. 1 miles D. e~%
<br />ilryCedarCreer 5.1 III11e, 1.04;;
<br />
<br />There Jxe other :;'"J~l r~ser'loirs sCJtter~G thrcugh th~ DJsins, ;ir~.
<br />r.larilyforstocl<wdterlng. The size, location and CQndition of these
<br />reservoirs indicate their millirnal Jffect on basin hydraulics.
<br />
<br />C. Study Reaches
<br />The study reach for Cedar Cre€k lies between the existing Montrose
<br />Water Treat,"ent Plant, ~nd the stream's cOllfl uen~e \'lith the UncUlllpalogre
<br />River. In the non-urbaniz€oareas, CedJrCreek ischarJcterizedby
<br />arroyotypechannelsectionsofsignificantCclpacitywithr~erately
<br />""dVY uv~rl>d"~ vegeldt i...". ;;itil in ti,.. U,-bd'll l~u dr-"d, U,,, nJdU
<br />crossings are usually limited incapacity. O~bris is generated froln
<br />scrubOclk and sagebru,h plus overbankvetetatlon.
<br />
<br />O. Urllan Draina'le Analysis
<br />F i !Jure I [-2 ill ustrales the I~ont rose Water Servi ce "rc", the city
<br />linitsofMontrose, dnd the Urban DroinagQAnalysis Area. The City of
<br />Montrose is rapidlyexj)andins inall directions, as indicated by the
<br />extentoftllCl<ater,ervicearea.
<br />
<br />The study redch for Montrose Arroyo llclS itSUfJstrecllTI
<br />Ogden ROJd, dpprcximately2miles soutlleast of the city.
<br />dD~'nstrea'n l1mit is at the s:::rcdm's confl uence with Cedar'
<br />
<br />limit near
<br />Th'
<br />Creek.
<br />
<br />Hie area covered by the urban dra 1 n~ge ana Iys 1 s 1 S 4,Jb4 acres, or
<br />dp~"oxi"lat~ly G.8 square lI1il es. The boundaries of thi s area were
<br />defi ned based on extent of mapping and tfl~ d~gr~e of re-asonably ~rox-
<br />ilnate uriJan expar.sion for the area predGl'Iinantlynortheast 0 fthe
<br />Uncompahgre River. 'i~ure !1-2 illustrate, the urban drainage analysis
<br />in detail.
<br />
<br />-12.
<br />
<br />.13-
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