FLOOD04012

• Designation Number: 184
• County: Jefferson
• Community: Unincorporated Jefferson County
• Stream Name: Bear Cree, Mt. Vernon Creek, Sawmill Gulch, etc.
• Basin: South Platte
• Title: Flood Hazard Area Delineation - Southern Jefferson County
• Date: 12/1/1981
• Designation Date: 2/5/1982
• Floodplain - Doc Type: Floodplain Report/Masterplan

I

I

I

Other Floods: The storms of July 7, 1933 and September 8, 1934

which produced floods mentioned in the section on Bear Creek also

produced floods of unknown magnitude on Mt. Vernon Creek.

FACTORS AFFECTING FLOOD HAZARD

I

Factors Which Increase the Flood Hazard:

I

- Sawmill Gulch

Flood of July 7,1933: The cloudburst which produced flooding on

Bear and Mt. Vernon Creeks also produced a flash flood on Sawmill

Gulch. No information concerning the peak flow of this flood on

Sawmill Gulch was found.

I

- Turkey Creek

Natural impediments to flood flow include brush, trees and other

vegetation which naturally grow along stream banks and lowlands

adjoining drainageways. During floods, vegetation tends to decrease

the flow velocities and, as a result, cause backwater conditions that

increase flood elevations. During periods of high flood flows, the

natural vegetation found within the flow area is often uprooted and

carried by the floodwaters until it is collected at bridges, culverts

or other man-made obstructions. In addition to the vegetative

material floodwaters tend to erode channel banks and carry the
,

suspended soil material, as well as rocks and boulders, adding to the

debris. As these masses of debris accumulate and impound larger

volume of water, the artificial barrier eventually breaks loose and a

wall of water and debris surges downstream increasing the hazard and

I

I

The highest peak flow recorded on Turkey Creek was 1,200 cfs

on August 24, 1946. The gaging station, which operated from 1943

to 1953, was located 2 miles upstream from the confluence of

Turkey and Bear C-reeks. However, comparison of the flows re-

corded at the Morrison and the Sheridan gages on Bear Creek,

which are upstream and downstream, respectively, of the con-

fluence with Turkey Creek, indicates that flood flows occurred on

Turkey Creek in 1957, 1965, and 1969.

destruction.

I

I

I

I

- Deer Creek

In general, both natural and man-made obstructions exist which

tend to restrict flood flows and to cause overbank flooaing. These

obstructions will often result in unpredictable flood flow patterns.

Some obstructions also tend to become sources of debris and further

obstruction when dislodged from their normal locations. Also,

obstructions tend to concentrate flood flows which in turn result in

increased velocities and increased hazards in adjacent areas.

I

A gaging station located on Deer Creek approximately 3.5

miles downstream from the mouth of the South Fork operated from

1942 to 1946. During this period, no high flows were recorded,

and no additional information concerning floods on Deer Creek was

found.

I

I

- Parmalee Gulch

It is impossible to predict the degree of accumulation of debris
in floodwaters and the resulting effect of such accumulation. It was
assumed in this report that the existing structures in the path of
flood flows would not see blockage and reduced flow capacity during
the occurrence of a flood event.

No information concerning floods on Parmalee Gulch was found.

I

I

I

I

-4-