FLOOD01407

• Designation Number: 301
• County: Arapahoe
• Community: Unincorporated Arapahoe County
• Stream Name: Piney Creek Tributaries
• Title: Flood Hazard Area Delineation - Piney Creek Tributaries
• Date: 4/1/1989
• Designation Date: 7/1/1989
• Floodplain - Doc Type: Floodplain Report/Masterplan

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The Antelope Creek 100-year floodplain is narrow and confined to
the channel area along most of the study reach, with top widths
generally ranging from 50 to 100 feet. There are some areas where
the floodplain is wider due to ponding behind the existing road
crossings and pond embankments. The spreading of flows that
occurs when these roads are overtopped, or the flood waters spill
out around the pond embankments, also increases the floodplain
with, and causes areas of shallow flooding. The depth of flow at
the channel thalweg varies from as shallow as 1 foot along some of
the steeper channel reaches, to as deep as 11 feet when ponding
behind the Long Avenue road embankment. The only inhabitable
structures that are presently in the 100-year floodplain are 7
homes located in the shallow flooding area just west of Antelope
Creek between Arapahoe Road and Piney Creek. The flooding depth
in this area should not exceed one foot. The horse barns and
utility sheds associated with these 7 homes are also in this
shallow flooding area. In addition, one shed located approximately
2,100 feet south of Arapahoe Road is in the 100-year floodplain on
Antelope Creek.

The Tenderfoot Gulch floodplain averages approximately 100 feet in
width, varying from 25 feet up to over 400 feet at the confluence
with Piney Creek. Flooding depths range from 1-1/2 feet to 10
feet at Inspiration Drive where flows overtop the roadway.
Backwater due to the road embankment affects the Tenderfoot Gulch
floodplain for nearly 1,000 feet upstream. There are homes along
the channel throughout the study reach, however, they are located
well above the floodplain elevations. One small storage building
is within the 100-year floodplain near the lower end of the study
reach.

FLOODPLAIN DESCRIPTIONS

The Sampson Gulch floodplain ranges from as narrow as 20 feet in
the upstream portion of the study reach between Otero Drive and
Piney Lake Road to as wide as several hundred feet near the
confluence with Piney Creek. The 100-year flood depth averages
approximately 3 feet for much of the study reach. Depths of less
than 2 feet occur along the steepest areas. Ponding to a depth of
10 feet occurs upstream of Otero Drive, although the roadway is
not overtopped. The only existing development in the basin is in
this vicinity, however, all structures are well above flood
elevations.

The 100-year floodplain for South Saddle Rock Ranches Gulch from
the confluence with Piney Creek upstream to Station 78+50 is wide
and shallow with widths generally ranging from 70 to 150 feet.
Flood depths in this reach range from 2 to 4 feet. Upstream of
Station 78+50, the 100-year floodplain is more uniform with an
average width of about 60 feet and an average depth of about 3.5
feet. There are no structures within the 100-year floodplain.

The South Saddle Rock Tributary floodplain is quite narrow
throughout the study reach. Floodplain widths range from 10 feet
to 55 feet and depths range from 1 to 3 feet. The channel bed,
which is deeply incised, has a slope that exceeds 3% for most of
the reach. The existing land use in this area is ranching and
there are no structures within the South Saddle Rock Tributary

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