FLOOD05380

• County: Summit
• Community: Frisco, Silverthorne, Breckenridge
• Stream Name: Snake River, Straight Creek, Tenmile Creek
• Basin: Colorado Mainstem
• Title: Hydrology Report Flood Insurance Study Summit County
• Date: 8/25/1978
• Prepared For: Summit County
• Prepared By: Gingery Associates, Inc.
• Floodplain - Doc Type: Floodplain Report/Masterplan

Below 9,000 feet, sage usually covers the valley walls. The
floodplains and valley floors are generally covered with
thick willow bushes up to the river channels.

Dillon Reservoir, which lies in the center of the basin,
is the only man-made diversion that appreciably effects
peak runoff rates, and only on the Blue River below Lake Dillon.
The Blue River channel slope varies from 4.6% above
Breckenridge to 1% below Lake Dillon.

The Snake River Basin forms the easternmost section of the
Blue River Basin. It drains in a westerly direction, from
an elevation of 14,270 feet at Grays Peak along the Continental
Divide south of Loveland Pass, to Dillon Reservoir at an
elevation of 9,000 feet. The basin is approximately 7 miles
wide throughout and 12 miles long with a drainage area of
76 square miles at Dillon Reservoir. The channel slope
ranges from 5.7% in the upper basin above the Town of
Montezuma to 1.1 % in the study reach near Keystone. (.Figure I).

The Straight Creek Basin lies just north of the Snake River
Basin and drains in a southwesterly direction from an elevation
of about 12,500 feet above the Eisenhower Tunnel. It empties
into the Blue River just below Lake Dillon near Silverthorne
at an elevation of 8,800 feet. The basin has a uniform
width of approximately 3 miles. It is 8 miles long with a
drainage area of 20 square miles at the mouth. The channel
slope ranges from 3.4% in the study reach to a steep 7.7%
in the upper basin. (Figure I)

Tenmile Creek flows north to northeast into Lake Dillon from
the Fremont Pass vicinity. This basin parallels the Upper
Blue River basin with the Tenmile Range dividing the two. The
western boundary of the basin is formed by the Gore Range
and Vail Pass, and the southern boundary is the Continental Divide.
The upper basin is characterized by an open rolling terrain.
In contrast, the lower basin consists of the narrow winding
Tenmile Canyon. The total drainage area is 94 square miles at
Frisco, 35 square miles in the upper basin above the confluence
with West Tenmile Creek. The basin width is 7 miles and the
total basin length is about 14 miles. The Creek slopes at
about 1.4% at Frisco, 2% in the canyon, and 2.7% in the upper