FLOOD01718

• County: Montrose
• Community: Montrose
• Stream Name: Uncompahgre River
• Title: City of Montrose Flood Control and Drainage Plan
• Date: 5/1/1981
• Prepared For: Montrose
• Prepared By: Gingery Associates, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

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Tht neilrlwaters of Dry Cedar Creek lie apPr'Oxirr..ately ten miles southeast
of Montrose at an elevation of approximately 9.400 feet. The stream flows
in a generally northwesterly direction to its confluence with the Uncompahgre
River ont mile soutr. of the City. Dry Cedar Creek has a catchment area of
approximoltely 21.9 square miles.

TABLE 1
DRAINAGE BASIN CHARACTERf~TICS
Elevation ~Ft. MSL) length Basin Area
Stream Headwaters onfluence (Mi) (SQ. Hi.)
Cedar Creek 9400 5700 24.8 56.3
t~ontrose Arroyo 7500 5760 10.5 17.8
Dry Cedar Creek 9400 5800 14.3 21.9

ExistinQ Drainage Systems
The .oLation, sile, and type of structure on Cedar Creek and Montrose
Arroyo are shown in Flgllr'{> 2. These crossings art generally adequate only for
discharges up to the 5-year frequency storm. As a result, large portions
of the City of Montrose are susceptible to significant flooding during t~e
less frequent storms, particularly if blockage of the crossings occur.
Stream crossing capacities are listed in Table 2.
Urban drainage in the City of ~~ntrose relies primarily on the exist-
ing street system for conveyance of 10caliled runoff. The existing storm
sewer system Is not extensiv~ and was not the result of long-range, area
wide planning and is, therefore,nottotallyconsistentthroughoutwlth
regard to hydrologic considerations.
Where storm sewerlng is provided in Montrose, the inlets are fre-
Quently located so as to be incapable of interceptingthedrainag e. In
addition. many of the inlet drain lines are 8" diamet~', f1ipes which easily
clog with debris carripd by the storm runoff. llUlllero,;:, ~eCl ions of tile

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stormse",ersystell".ilfetoosmall to carrysignific"nt flow. Virtually none
of t~e existing storm sewers provided within the City are adequate to in-
terceptandcOnveytherunoffgeneratedbythe5-yearfrequencystorm. A
S'Jnn;!ry of the existing storm sewer systefflS olnd limitiny cill'<lcities are
listed in Table 3.
The street curb and gutter system functions as the primary drainage
system for the urbanized part of ~ontrosc. The streets have various con-
veyance capacitie~ due to varying cross-se~tions, crown slope, and presence
(or lack) of curb and gutter. Additionally, successive asphalt overlays
o~er the years have further limited street carrying capacity. These fac-
tors contribute to the need for a larger storm sewer system than otherwise
would be necessary were the street section reasonably uniform and houses
placed well above the top of the curb.
The street system is generally inadequate to contain the 5-year storm
runoff at a flow depth less than the curb height (6~), which is the standard
basis for design (Reference 1).
A map of the existing sco~ sewer is shown in Figure J.

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