FLOOD05699

• County: Jefferson
• Community: Idledale, Morrison, Tinytown
• Stream Name: Sawmill Gulch, Bear Creek, Mt. Vernon Creek
• Basin: South Platte
• Title: Flood Hazard Area Delineation
• Date: 12/1/1981
• Prepared For: Jefferson County
• Prepared By: UDFCD
• Contract/PO #: &&
• Floodplain - Doc Type: Floodplain Report/Masterplan

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Morrison which were prepared by the U. S. Army Corps of Engineers,
Omaha District.

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feet above mean sea level. The basin has an area of 158 square miles

at Idledale below Sawmill Gulch, 164 square miles at the Morrison Gage

and 175 square miles at Morrison below Mount Vernon Creek. The

average slope of the streambed is 2 percent and critical or super-

critical velocities will occur on most of the reaches studied. The

flooding hazard, due to residential development in the floodplain and

several undersized bridges, is high.

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STUDY AREA DESCRIPTION

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The study area comprises the following reaches in the southern

part of Jefferson County (see Sheet 1 for locations):

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- Sawmill Gulch: Approximately 1.70 miles extending upstream from its
confluence with Bear Creek in Idledale.

Mount Vernon Creek, a left bank tributary of Bear Creek, has its

headwaters near Genesee Mountain and Highway 70. Mount Vernon Creek

flows in an easterly direction along Highway 70 to the Highway 26

junction, and then turns south to flow between the foothills and the

hogback toward Morrison. Elevations in the drainage basin range from

5700 feet to over 8200 feet (MSL). The basin has an area of 6 square

miles at the upstream end of the study, and approximately 10 square

miles at its confluence with Bear Creek in Morrison. The average

slope of the streambed is 3 percent and supercritical velocities will

occur along the entire reach studied. In Morrison, the flooding

hazard is high due to residential development in the floodplain and

several undersized bridges. Upstream of Morrison, development has not

yet taken place and the floodplain is narrow.

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- Bear Creek: Approximately 1.04 miles extending through Idledale.

Approximately 1.65 miles extending through the city

of Morrison and upstream of Bear Creek Reservoir.

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- Mount Vernon Creek: Approximately 2.50 miles extending upstream

from its confluence with Bear Creek in the city

of Morrison.

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- Parmalee Gulch: Approximately 3.37 miles extending upstream from its
confluence with Turkey Creek.

Sawmill Gulch is a small left bank tributary of Bear Creek drain-

ing an area of approximately 2 square miles north of Idledale. The

elevations in the basin range from 6500 feet to over 7900 feet (MSL).

The average slope of the streambed is 5 percent and supercritical

velocities will occur along the entire reach studied. Sawmill Gulch

flows in a southerly direction toward Idledale in a deeply incised

valley, and the impact of a 100-year flood on the existing residential

development is practically nonexistant.

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- Turkey Creek: Approximately 1.59 miles extending through Tiny Town.

Approximately 2.14 miles, upstream of Bear Creek

Reservoir.

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Bear Creek, a left bank tributary of the South Platte River, has

its headwaters near Mount Evans in Clear Creek County and flows in an

easterly direction toward Bear Creek Reservoir and the City of Denver.

Elevations in the drainage basin range from 5700 feet to over 14000

Turkey Creek, the major right bank tributary of Bear Creek, has

its headwaters in the vicinity of Aspen Park in Jefferson County.

Turkey Creek flows in a northerly direction to Tiny Town and then

turns east along Highway 285 toward Bear Creek Reservoir. Elevations

in the drainage basin range from 5800 feet to over 10600 feet (MSL).

The basin has an area of 44 square miles above Parma lee Gulch and 50

square miles at the downstream end of the study reach. The average

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- Deer Creek: Approximately 3.67 miles, upstream of Chatfield Lake
State Recreation Area.

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