FLOOD06100

• County: Statewide
• Community: State of Colorado
• Basin: Statewide
• Title: Design of Stable Channels with Flexible Linings
• Date: 10/1/1975
• Prepared By: Hydraulics Branch, Federal Highway Adminstration
• Floodplain - Doc Type: Educational/Technical/Reference Information

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v. Composite 'Channel LinirtgDesi~

The methods of this circular may be used for the design of
channels lined with more than one material. The most cOllllllOn
composite channel is a grass lined channel with a concrete
lining in the channel bottom. The smooth concrete liner
greatly increases the capacity of the channel, while the
grass lined channel sides provide freeboard.

The junction of two materials with different resistance to flow
is critical due to the development of secondary currents at the
shear zone. Such junctions should be carefully installed, and
dmax for the weaker material should be chosen conservatively.

VI. Design Charts

The following design charts comprise the figures to determine
the maximum permissible depth of flow (dmax- So Charts) and
the hydraulic resistance (V - R Charts) for the various lining
materials. In addition, there are design charts for rock
riprap lined channels with side slopes steeper than 3:1 and
with bends, and one example capacity chart for a concrete
lined trapezoidal channel.

Freceding the design charts is a brief description of each
lining material. The descriptions are not meant to be
complete specifications; however, they should be adequate
for the designer to determine whether the lining material
for which the design curves have been prepared is the same
as the material available to him. If the material is
significantly different, the design charts of this manual
should not be used.

Channel Geometry

Chart 1 is an illustrative example of a geometric design aid
for trapezoidal channels, either symmetrical or unsymmetrical.
Similar charts may be developed for other channel geometries
such as parabolic channels. Geometric tables and the equations
for a variety of channel shapes are given in the MSU report (3)
and Appendix B.

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