FLOOD06258

• Designation Number: 25
• County: Mesa
• Community: Grand Junction
• Basin: Colorado Mainstem
• Title: Floodplain Information Report - Colorado and Gunnison River, Grand Junction, Colorado
• Date: 3/1/1973
• Designation Date: 10/1/1973
• Floodplain - Doc Type: Floodplain Report/Masterplan

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The Colorado RIver rIses hIgh in the Rocky Mountains of central
Colorado on the west sIde of the ContInental DIvIde and flows west and
south through the State of Colorado. The Gunnison RIver also rises hi9h
In the central Rockies and is the princIpal tributary to the Colorado
River In Colorado. The Colorado River has a drainage area of about
8,900 square miles upstream from Grand Junction, and the Gunnison River
has a drainage area of about 8,000 square miles above Its mouth.

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The broad val ley of the Colorado RIver from PalIsade to Mack,
known as Grand Val ley, Is bounded on the north by the Llttie Book ClIffs
and on the south by the Uncompahgre Plateau. The clIffs and plateau
rIse abruptly about 2,700 feet above the river. The Colorado River
flows along the south side of Grand Junction and Intercepts several
minor drainage courses or washes in the study area. The largest of
these are IndIan Wash on the north side of the river and No Thoroughfare
Canyon and Red Canyon on the south side. IndIan Wash drains a portion
of the Little Book CI iffs and flows across the broad Grand Val ley In a
shal low channel to enter the Colorado River just east of Grand Junction.
No Thoroughfare and Red Canyons are deeply incised In the Uncompaghre
Plateau and enter the flood plain of the Colorado River--No Thorough-
fare Canyon just upstream from the Grand Avenue Bridge and Red Canyon
just below Connecticut Lakes. The GunnIson River enters the Colorado
River from the south just west of the city.

The cl imate of the area is arid to semIarid except In the hIgh

headwater areas where precipitatIon is moderately heavy. Average pre-

cipitation at Grand Junction Is about 8 inches per year. In high

mountain areas the average precipitation exceeds 40 Inches per year,

much of wh I ch occu rs I n the form of snow. Me I t from the mounta I n snow.-

pack is the source of the often flood producing late spring-early sum~lr
runoff. Temperatures in Grand Junction range from the high nInetIes in
the summer to below zero in winter, with occasional highs exceeding 100
degrees and lows to 20 deqrees below zero.

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