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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and differ from bridges in that the top of the culvert does not
normally serve as a road surface. These facilities provide
an unnatural barrier to the natural conveyance of flood flows.
As a result, special consideration and analysis are required
at these flood plain crossings.

4. Transitions to and from channels and culverts and
sloping wingwalls.
5. Culvert length.
6. Limitations on overflow depths for various street
types (collector, arterial, etc.), as provided in
the USDCM.

11

The design of culverts shall be in accordance with acceptable
engineering practice as outlined in the USDCM. Design must
consider the hydraulic characteristics of inlet and outlet
control, special inlet design, transitioning from and to natural
channel flow, materials and structural aspects as well as
consider overtopping of culverts and the hydraulic effects on
other facilities.

Operations and Maintenance Considerations

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Energy dissipators may b~ required where excessive velocities
are developed at culvert outlets due to high inlet heads or
steep slopes. The purpose of the energy dissipator is to reduce
the high culvert velocity to acceptable channel velocities
at culvert outlets so as to prevent scour and erosion. Such
structures will usually consist of an impact barrier at the
downstream end of the culvert or special turbulence generators
located within a heavily lined and protected energy dissipation
basin.

Upon completion of construction of any channel improvements,
a maintenance program will be needed to assure that design
conditions exist prior to flooding. The Van Bibber Creek
maintenance requirements will be similar to those experienced
by many other municipalities and agencies which have undertaken
drainageway improvement programs.

The maintenance program should consist of general channel upkeep
including mowing, cleaning, repair of localized erosion and
replacement of riprap, and repair of roadway embankments after
overtopping. Grasses should be mowed to a length of 4-6 inches
to assure the planned flood flow depths and velocities during
a major flood event. Channels and culverts must be cleaned
to assure the availability of the full cross-sectional area
needed for the conveyance of a major flood.

Additional culvert design criteria include:

1. The selection of proper materials and roughness "n"
values for outlet control.
2. Consideration of velocity head and inlet type for
inlet control.
3. The selection of the proper "C" coefficient for weir
overflow considering headwall fences, trees, parked
cars and other overflow blockage types.

Reservoirs should be inspected at least once each year and
after each major runoff event to insure stability and the repair
of any minor erosion. Reservoirs may also have to be cleaned
periodically to insure the free operation of the outlet pipes
and to prevent major silting problems. Weep holes should be
cleaned to insure proper drainage around backfilled walls.

Maintenance costs for Van Bibber Creek, based on information