FLOOD02273

• County: Statewide
• Community: State of Colorado
• Stream Name: All
• Basin: Statewide
• Title: Hydraulic Design of Energy Dissipators for Culverts and Channels
• Date: 12/1/1975
• Prepared For: USDOT
• Prepared By: Federal Highway Administration
• Floodplain - Doc Type: Educational/Technical/Reference Information

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n.s. DEPARTHENT OF TRANSPORTATION

FEDERAL HIGHWAY ADM.INISTRATIOH

TIlE HYDRAULIC DESIGN OF EHERGY DISSIPATORS
FOR CULVERTS AND CHANNELS

Prepared by M. L. Corry, P. L. Thompson
F. J. Watts, J. S. Jones, and D. L. Richards

I. DESIGN CONCEPT

The failure of many highway culverts can be traced to
unchecked erosion. Erosive forces which are at work in
the natural drainage network are often. increased by the
construction of a highway. Interception and concentra-
tion of overland flow and constriction of natural waterways
inevitably results in an increased erosion potential. To
protect the highway and adjacent areas, it is sometimes
necessary to employ an energy dissipating device. These
devices cover a wide range in complexity and cost and the
particular type selected will depend on the assessment of
the erosion hazard. This assessment includes determining
the ability of the natural channel to withstand erosive forces
and the scour potential represented by the superimposed
flow conditions. The purpose of this circular is to aid
in selecting and designing an energy dissipator which will
meet the requirements indicated by an erosion hazard assessment.

Energy dissipators should be considered part of a larger design
system which includes the culvert, channel protection require-
ments (both upstream and down), and may include a debris
control structure. When viewed from this standpoint, much
of the input data will be available to the energy dissipator
design phase from previous design steps. For example, the
culvert design should provide: the design discharge; outlet
flow conditions--velocity and depth; culvert type--size,
shape, and roughness; culvert slope; operating characteristics--
performance curve; and the standard culvert outlet design
utilized--projecting, wingwalls, headwall, aprons, etc.

~uch of the location data will also s~rve more than one
design segment in the overall process. Vicinity and contour
maps are essential to culvert, dissipator and channel designs.
A debris assessment is a necessary input to selecting both
a debris control structure and energy dissipator. The allow-
able scour estimate, which is related to location, is a design
as well as a selection parameter.

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