Roadside Revegetation

PLANNING PHASE TWO: ASSESS SITE
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Are the roads treated with gravel during the winter for traction? If so, how much gravel
is annually applied? How far is it swept into the road shoulder or road corridor? Are the
gravels recovered by scraping the shoulders?
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Is fire an issue and will fire protection treatments include thinning of vegetation?
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What about salts or other non-herbicide contaminants?
This is a partial list, and every project will have its own set of questions. The more these issues
can be addressed early in the planning stage, the more effective the revegetation plan will be.
Mitigation for Road Maintenance Impacts
Blading for Erosion Control
Ditches at the base of steep cut slopes are depositional areas for rock and soil that have moved
down from the slopes above. The rock and soil may fill the ditches, disrupting the flow of
water in the ditch and creating potential road drainage problems during storms. Blading is the
removal of the material that has filled in the ditchline and is a normal maintenance procedure
for erosive cut slopes. This operation not only removes plants that were established in the
ditchline, but also destabilizes the surface slopes immediately above the ditch. This can affect
the revegetation of the entire slope. Mitigating measures include engineering design that
reduces slope gradients (see Section 5.6.6.2, Mitigating for Steep Slope Gradients) or changing
the road drainage system so that cleaning of ditches is not necessary. If neither measure is
possible, assess whether it is worth implementing revegetation treatments, since revegetating
unstable slopes is usually unsuccessful.
Herbicide for Vegetation Control
Contact the government agency responsible for controlling weeds or vegetation in the road
corridor and discuss its strategy for weed control. In areas where vegetation must be maintained,
signs can be issued to notify operators not to apply herbicides (Figure 5-71).
Graveling for Winter Safety
In areas where gravels are applied to road surfaces for traction during snow or icy conditions,
there will be a buildup of gravels on the sides of the road through sweeping of the road surface
or snow-blowing. Vegetation that has been established in these areas is often completely
covered with gravel when the snow melts. It is important to learn if the road maintenance
agency will recover this gravel for reuse or let it accumulate. If gravel is recovered, this area
will be in constant state of disturbance. Determine the salvage distance and consider the
revegetation stategies in this zone. In areas where gravels are not salvaged, select the species
that will survive and grow in this unique growing environment. One strategy is to select species
that respond favorably to being covered by gravels. These include species such as manzanita
and willows that root from their stems when covered by soil or gravel. Tap-rooted species,
such as lupines, can take advantage of such conditions because they can access moisture deep
in the gravel deposits (Figure 5-72). Examine shoulders of existing roads to identify species
that have adapted to these conditions and use these species for revegetating these areas.
Clearance for “Line of Sight” and Safety
Trees and shrubs are often thinned or removed in areas where line-of-sight is impeded. Good
communication with the government agency responsible for maintaining the road during the
planning phase will help identify those areas not suitable for shrub and tree species. Select
grasses and forbs or low growing shrubs (less than 2 to 3 feet tall) for these areas.
Protection of Utilities
Do not plant trees under or near utility structures, such as power lines. Discuss the planting
plans with the maintenance agency to find out if other utilities need protection.
Figure 5-70 | Chemical control
of roadside vegetation
Road maintenance treatments for
control of vegetation include the use
of herbicides on roadsides. There is no
need to seed these areas if they will be
treated chemically. A meeting with road
maintenance personnel to understand
how roadside vegetation will be managed
can reduce revegetation costs and
benefit pollinator species.
Figure 5-71 | Road signs
identify areas to protect
Placing no-spray signs is a method of
identifying areas to protect from herbicide
application.
Roadside Revegetation: An Integrated Approach to Establishing Native Plants and Pollinator Habitat
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