Lance
Landscape develops & installs various stabilization and restoration systems,
depending on the situation, in order to achieve slope stabilization. Slope
stabilization methods include anchoring systems of rock bolts, rock anchors,
tiebacks, tiedowns, earth anchors, soil nails, concrete anchors, &
post-tensioned tendons.
Slope stabilization becomes necessary when soil moisture, erosion, or any sort
of ground movement causes the foundation to become unstable. There are many
factors that come into play when deciding how slope stabilization should be
achieved.
We have years of experience in achieving the goals of our clients using the best
possible methods for slope stabilization.
Successful restoration of slope failures requires understanding the regional
geology, vegetation conditions, water management and geotechnical engineering
issues. To ensure long term success of the slope stabilization, the methods must
also consider the surrounding human impacts and address urban runoff and view
corridor management.
Three critical components are necessary for successful restoration of a failed
or threatened slope. The first is a technical understanding of the source of the
failure and team evaluation of means and methods to stabilize the condition. The
second is an assessment of the natural vegetative conditions of the slope and
design of a restoration plan that enhances the stability and mends the habitat.
The third and most often neglected element of a successful plan is understanding
the human context of the restoration.
Vegetation can serve several purposes in stabilization projects, both a primary
source of stabilization and as native habitat and greenbelts. The primary ways
the establishment of vegetation reduces the potential for slope erosion are:
- Plant roots, both large and small, provide a fibrous web
that stabilizes and anchors the soil
- Plant cover intercepts rain, reduces the direct impact of
rainwater on the ground surface and protects from surface runoff and
erosion. Dense groundcovers and grasses reduce runoff velocity and act as a
filter trapping soil that would be washed downslope
- Vegetation and associated plant litter filter the
transport of soil moisture. Plants can play an important role in dewatering
unstable slopes. Soil moisture is drawn up through roots and into plant
leaves where transpiration releases it into the atmosphere.
The foundation of successful slope vegetation
restoration is identifying the composition of the native plant community and
carefully considering the mircoclimate of the slope. Plants selected for the
revegetation should mimic the native species composition in both type and
strata. Within forested slopes and ravines, the planting design should mend the
slide area with vegetation identified in the surrounding slopes to provide
continuity in the habitat.
The vegetation types and methods of slope plantings should
vary according to the location of the slide within the landscape of the bluff,
hillside or ravine.
Separate planting approaches should be used for the crest of the slope, where
vegetation acts to strengthen the soils and reduce erosion; the face of the
slope, where vegetation is used to resist shallow sliding and moderate surface
runoff; and at the toe of the slope, where vegetation is used to resist
downslope soil movement. Integral to the slope revegation plan is the planting
of the slope setback buffer.
The slope setback is often the first zone of conflict between the need for slope
stabilization and the desires of property owners. Human use is a large
contributor to most landslides in residential areas. Home owners and businesses
clear trees and debris to open and maintain views and often deposit cleared
debris over the bank of the slope. Trails and stairs are cut into the steep
banks for ready access to streams and beaches. Lawns and patios are built up to
the edge of the bank, affecting the long-term stability of the slope.
Because humans are the prime threat to stable slopes, revegetation plans must
consider human use. Even the most viable plant community will be strained to
accommodate beach access and view maintenance. The planting design needs to
create a long-term plant community that balances the needs of the stabilization
with the adjoining neighborhoods.
Plant selection should consider mature growth limits and opportunities to
incorporate access routes into the stabilization design. To increase the
viability, the management plan must be developed with the input of the
surrounding neighborhood. Active participation in maintenance of the adjoining
slope will not only increase the success of the restoration efforts but also
provide an early warning system for any future problems.
Mitigation efforts to reduce future slope failure begin with early
identification of signs of instability, repair of surface drainage systems that
may be creating downslope erosion, relocation of uses that are encroaching into
slope setbacks and planting stabilizing vegetation to reduce surface erosion.
Management of unstable slopes is dependent on public information and
involvement.
