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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u. S. DEPARTMENT OF TRANSPORTATION

Federal Highway Administration

DESIGN OF STABLE CHANNELS WITH FLEXIBLE LININGS

By

Jerome M. Normann

I. Introduction

One means of reducing erosion on the right-of-way during highway
construction and operation is through the use of properly designed
linings in drainage channels. Linings may be rigid, such as
portland cement or asphaltic concrete, or flexible, such as
vegetation or rock riprap.

Flexible linings of erosion resistant vegetation and rock riprap
should be used whenever feasible. When vegetation is chosen as the
permanent channel lining, it may be established by seeding or
sodding. Installation by seeding usually requires protection by
one of a variety of temporary lining materials until the vegetation
becomes established.

While vegetation and rock riprap linings have been used for many
years, in most cases the success or failure of the lining has been
a matter of chance, and design information has been limited or
difficult to apply. This circular presents design methods developed
from recent research results for temporary linings, vegetative
linings and rock riprap linings.

Flexible linings are generally less expensive to install than rigid
linings, provide a safer roadside, and bave self-healing qualities
which reduce maintenance costs. They also permit infiltration and
exfiltration, have a natural appearance, especially after vegetation
is established, and provide a filtering media for runoff contaminants.
Vegetative and rock riprap liners provide less improvement in
conveyance over natural conditions and the resultant acceleration of
flow volume and peak is less than with rigid liners.

Flexible linings do have the disadvantage of being limited in the
depth of flow which they can accommodate without erosion occurring.
As a result, the channel may provide a low capacity for a given
cross-sectional area when compared to a rigid lining. Also limited
.right-of-way, unavailability of rock, or the inability to establish
vegetation may preclude the use of flexible linings. In these
1nstances, rigid linings may be the only alternative.

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