Roadside Revegetation

IMPLEMENTATION GUIDES
To avoid this problem, several important measures should be taken when installing erosion
mats. First, the surface of the soil must be smoothed to a uniform elevation before the mat is
placed. This will assure that when the mat is pinned to the soil, it is in intimate contact with
the soil surface. Second, the materials must be trenched or keyed into the soil at the upper
reaches of the fabric. This will assure that the material does not move downslope. Third, as
with all slopes being revegetated, concentrated water should be kept off these slopes.
Seeds must be sown on the site prior to installing erosion mats. This can be done using any
type of seeding method (e.g., hydroseed, drill, or hand broadcast). Care must be taken during
and after mat installation to avoid disruption of the seedbed. Unless the seeds are extremely
small, sowing seeds over installed erosion mats is not recommended because larger seeds
will hang up in the fabric. Small seeds can be applied over erosion mats if tackifiers are not
used and if the timing is such that sufficient rain will likely move it through the erosion mat
to the soil surface.
Some manufacturers offer erosion mats that are impregnated with seeds, eliminating the
need for sowing. This method is advantageous on steep slopes or soil-faced gabion walls (see
Inset 10-3) where placing seed prior to mat installation is very difficult. It is important to work
directly with companies that provide these products by supplying them with source-specific
seeds and specifying appropriate sowing rates. For successful germination, seeded erosion
mats must be installed so that the seeds and fabric are in direct contact with the soil and strict
quality control measures taken.
Inset 10-3 | Case Study: Erosion mats with native grasses and forbs
Straw and hay are long-fibered mulches used on many revegetation projects for seed cover and erosion control (Figure 10-18E). The terms
straw and hay are often used interchangeably. However, straw is the stubble left over after seeds have been harvested from commercial seed
or grain crops; hay comes from grass/legume fields usually grown for feed. When hay is harvested, it usually contains seeds from a variety
of pasture species.
Reconstruction of the Agness-Illahe Highway required the construction of long sections of gabion walls. Since this highway is visible from the
Rogue River (a designated “wild and scenic” river in southwestern Oregon) and is heavily traveled for recreational purposes, it was important
that the gabion walls be visually screened using native plants. Gabions were designed to hold 12 inches of compost-amended soil (topsoil was
not available) on the face of the walls by wire mesh frames (Figure A). Placement of seeds at the surface of the gabion wall was problematic.
Several small plots using different erosion mats, seed mixes, seed rates and seed-attaching methods were tested to determine how to best
meet the revegetation objectives (Figure 10-21).
The results from these trials indicated that we could attach native
grass and forb seeds to erosion mats using a tackifier (B). In 2003,
we applied our findings to the construction project. Needing
approximately 33,000 ft2 of gabion wall facing, we prepared
the erosion mats by rolling them out on a road surface, applying
California fescue (Festuca californica), gluing the seeds to the
mat, and re-rolling the erosion mats.
The seeds held tightly to the fabric during transportation and
handling. At the construction site, seeded mats were attached to
the wire mesh at the face of the wall (C) and compost- amended
soil was placed behind the screen and lightly tamped. The gabion
walls were built in the summer of 2003, but the seeds did not
germinate until late fall after several rainstorms. Figure D shows a
close up section of wall with newly germinating seedlings coming
through the erosion mat in late 2003, four months after wall
construction. Figure E shows 20 to 30 ft high walls in July 2006,
three years later, fully vegetated and effectively screening the
walls from the road and river (Photo C courtesy of Scott Blower).
A
D
Compost
Amended
Soil
Wire Mesh
Frame
B
C
E
Roadside Revegetation: An Integrated Approach to Establishing Native Plants and Pollinator Habitat
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