FLOOD07780

• County: Eagle
• Community: Eagle County
• Basin: Colorado Mainstem
• Title: Hydrology Addendum FIS - Eagle County Unicorporated Areas
• Date: 2/1/2002
• Prepared For: CWCB
• Prepared By: Montgomery Watson Harza
• Floodplain - Doc Type: Floodplain Report/Masterplan

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STUDY AREA DESCRIPTION

Community DescriDtion
Eagle County, which is almost entirely rural, is located in west central Colorado. It has an area
of 1,686 square miles. The county is bordered by Routt and Grand Counties on the north,
Garfield County on the west, Pitkin and Lake Counties on the south and Summit County on the
east. Elevations range from 6,150 feet in the Colorado River Valley to over 13,000 feet on some
mountain peaks. Eagle is the County Seat of Eagle County. The Colorado Division of Local
Government Demography Section estimated the population of Eagle County as 41,659 in April
of 2000. The area covered by the FIS includes only the unincorporated areas of Eagle County.

Watershed DescriDtion
The Eagle River basin covers 57 percent, or 990 square miles, of Eagle County and, excluding 14
square miles, is contained entirely within the county. It drains in a northwesterly and westerly
direction, through the center of the county to the Town of Dotsero, where it joins the Colorado
River.

The Lower Eagle River is separated from Colorado River by Castle Peak on the north, and from
the Fryingpan River basin by Red Table Mountain on the south. The topography is characterized
by rolling hills and a wide valley floor. Vegetation in the basin is less dense in the lower reaches
than in the upper reaches. Elevations vary from 11,785 feet at Red Table Mountain to 6,120 feet
at the mouth of the river. Significant development has occurred throughout the Eagle River
Valley, especially near the Town of Avon. The upper Eagle River basin, which runs from just
above Gore Creek to the Continental Divide, is oriented toward the northwest and is bounded on
the west by the Sawatch Range and the southern Gore Range separates it from Gore Creek basin
on the east. The high point in the basin is Mount of the Holy Cross with an elevation of 14,005
feet. The upper portion is open, rolling terrain. In the lower reach, near the Town of Minturn,
there are some steeper mountain walls. In the Eagle River basin, commencing at approximately
8,500 feet, mixed aspen-pine forests are prevalent up to the timberline at 11,500 feet, where
alpine vegetation begins. Below 8,500 feet, sage and other types of scrub bushes provide a less
dense cover, with cottonwood trees in the floodplain along many streams. Above 8,500 feet,
willow bushes are found along the floodplain.

The Fryingpan River flows west from the Sawatch Range to the Roaring Fork River at the Town
of Basalt. Through the study reach, it has a moderately steep, shallow, and wide channel. The
vegetation along the floodplain consists of cottonwood trees and grass in the upper reaches. The
channel is generally rough with many cobbles.

The Roaring Fork River originates in the Sawatch Range at an elevation above 14,000 feet,
travels approximately 37 miles to the Town of Basalt, and flows on the west side of the town. At
the confluence of Roaring Fork and Fryingpan Rivers, 53 percent of the total drainage of the
Fryingpan and Roaring Fork River basins has been collected.

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