FLOOD03463

• Designation Number: 72
• County: Adams
• County: Arapahoe
• County: Douglas
• Community: Denver Metro Region
• Stream Name: Van Bibber Creek
• Basin: South Platte
• Title: Major Drainageway Planning - Van Bibber Creek
• Date: 3/1/1977
• Designation Date: 7/1/1977
• Floodplain - Doc Type: Floodplain Report/Masterplan

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For public protection and welfare, this area should also be
publicly acquired. Approximately 9 acres would be a part
of the flood prone area acquisition.

Many of the existing structures through the lower reach of the
project are not removed from the 100-year flood plain by the
construction of the Ward Road Dam and the proposed channel and
conduit improvements, therefore, localized flood proofing measures
should be implemented around many of these buildings. These measures
might consist of concrete block flood walls constructed to an
elevation at least l' above the 100-year flood elevation or approxi-
mately two feet above existing grade. The walls may be designed
to serve as planters or benches. Walk-over ramps could be provided
in the walls where needed. The location of the flood proofing walls
is shown on Sheet 18.

A new V-shaped channel should be constructed between Stations
26+00 and 46+00, with a maximum depth of approximately 6 feet and
4:1 side slopes. A 4' concrete trickle channel will be required
to eliminate ponding during low flow periods and the side slopes
should be grassed. The existing driveway culvert near Station
39+80 should be lowered to the proposed channel thalweg and tied
down with the construction of headwalls. A 35' x 5' concrete box
culvert with wing walls and headwalls will be required at Kipling
Street. Also, the street should be lowered to permit excess flood
flows to pass across the street and return directly to the main
drainageway.

Between Stations 22+00 and 25+00, the plan calls for a new
5' x 4" x 5' x 4" concrete box culvert to be constructed with a
side tapered inlet at Station 25+00. The inlet should be designed
for a culvert capacity of approximately 300 cfs or the capacity
of the existing Arvada Plaza Shopping Center culvert. The existing
60" reinforced concrete pipe between Stations 23+00 and 36+00
and the existing 72" corrugated metal pipe between Stations 22+00
and 23+00 would be removed. The dike called for near Station 25+00
is designed to direct flows in excess of 300 cfs north on to 58th
Avenue as well as easterly through the alleyway and also to eliminate
flooding in the residential area to the south. Also, flood proofing
walls are called for around those buildings within the shopping
center area with first floor elevations below the proposed 100-year
flood level. The existing sewer between Stations 6+00 and 22+00
would remain in place. The open channel between Stations 1+00
and 6+00 would be regarded to a "V"-shape with 3:1 side slopes and
a 4' concrete trickle channel. This channel section should be
modified as required to avoid conflicts with existing trees.

Upstream Limit of Study to South Tributary Confluence with
Main Channel: (Sheet 19 to 24) Located at the upper end of this
reach is Ramstetter Reservoir. This facility is presently on
record with the State Engineer's office and provides detention
storage reducing the 100-year peak from approximately 590 cfs to
540 cfs. The existing emergency spillway located at the south
end of the embankment is adequate and no improvements are needed.
This detention facility may be maintained as part of thp. Van
Bibber drainage system. This facility is not an essential part
of the Van Bibber Creek major drainage system, but does serve a
function for the minor flood events. Regardless, it is recommended
that no public liability be associated with the facility through
ownership or maintenance responsibilities.

The flood plain downstream from Ramstetter Reservoir is generally
quite narrow, ranging from approximately 50 to 150 feet in width.
Because velocities are generally quite low, between 4 feet and 9
feet per second, and because little or no development pressure
is anticipated along this reach, no general improvements are
required. Major crossings include the Boulder Canal which
presently flows over the Van Bibber Creek Tributary in a concrete
flume. The drainage structure waterway, approximately 130 square
feet, is large enough to pass the 100-year discharge beneath
the flume. This structure need not be replaced for hydraulic
reasons. Riprap protection should be provided on the channel bottom
and side banks at this structure.