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

FUTURE FLOODS

Although floods of the saMe magnitude as most of those that have

occurred in the past could recur in the future, discussion in this

report is limited to those designated as the Intermediate Regional

and Standard Project Floods. The Standard Project Flood, a rare

event, would be larger and would occur less frequently than an

Intermediate Regional Flood, but could reasonably be expected to

occur in the future. The most severe flood conditions on the Colorado

and Gunnison Rivers are likely to occur durinn the snowmelt runoff

season from late Apri I through June.

The flooding to be expected from drainage basins tributary to

the Colorado and Gunnison Rivers in the study area are not included

in this report because most are less than 2-3 square mi les in area

and as such are considered to be local drainaae problems. Of the

three larger drainages, Indian ~ash, which has been a flood threat

to Grand Junction, is now control led by a Soi I Conservation Service

project that affords protection aaainst runoff of Standard Project

Flood magnitude.

Debris collecting on bridge piers and deposition of si It in the

channel are not expected to cause reduction in channel capacity or

cause an increase in water depths (backwater effect) upstream of these

structures. Only the effect of vegetation normally existing in the

floodways were considered in preparing the maps, profi les, and other

illustrations showing the Intermediate Regional and Standard Project

Floods.

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