Design of Roadside Channels with Flexible Linings

This manual addresses the design of small open channels called roadside channels that
are constructed as part of a highway drainage system. Roadside channels play an
important role in the highway drainage system as the initial conveyance for highway
runoff. Roadside channels are often included as part of the typical roadway section.
Therefore, the geometry of roadside channels depends on available right-of-way, flow
capacity requirements, and the alignment and profile of the highway. The procedures in
this manual may also be used for ancillary roadside drainage features such as
rundowns.
Roadside channels capture sheet flow from the highway pavement and backslope and
convey that runoff to larger channels or culverts within the drainage system. This initial
concentration of runoff may create hydraulic conditions that are erosive to the soil that
forms the channel boundary. To perform reliably, the roadside channel is often stabilized
against erosion by placing a protective lining over the soil. This manual presents a class
of channel linings called flexible linings that are well suited for construction of small
roadside channels.
This manual is presented in dual units. The SI (metric) units precede the customary
units (CU) when units are given. Design examples are provided in both systems of
units.
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