Erosion control when skidding logs
This web article explains
how loggers and landowners can skid logs from the woodlot to a
road or landing while minimizing sediment runoff during a timber
Log skidding is a normal,
accepted practice in the Northeast. Unfortunately, it can lead
to severe soil erosion and destruction of standing trees that
forest owners would otherwise want saved.
After a tree is cut
and de-limbed, it must be moved through the forest to the landing,
where it will be loaded onto a truck for transport to the log
yard or mill. This process is called "skidding" because
the long logs (8 - 24 feet long) are chained to a machine and
dragged along the ground.
recent years, skidding machinery has become more powerful and
capable of driving up or down slopes that used to be off-limits.
Four-wheel drive, excess horsepower, and hydraulic steering have
made most forested areas accessible for skidding. With all this
power and capacity, this machinery also has the potential to create
erosion by tearing up forest soils. Along with forest roads, skid
trails appear to create more erosion potential than any other
timber harvest activity.
Crawlers and horse-drawn skidding
have less impact than conventional skidders, especially where
roads were first built for these "low tech" forms of
A lot of forest erosion from skidding
starts unintentionally. Logging crews tend to overlook the significance
of small, forested
stream courses and dry channels. These areas fill with fast-moving
water in the spring and after rainy periods. If the soil around
them has been disturbed, the edges quickly degrade and wash away.
Most skidding equipment is capable of driving through or directly
over small stream channels and dry washes. This disturbance is
now thought to be one of the main causes of declining forest soil
Forwarding is an alternative
to skidding. A forwarder is a combination mechanized arm and wheeled
cart. They carry logs out of the forest, rather than skidding
them. Forwarders can be equipped with tracks, in addition to rubber
wheels to minimize soil rutting and are considered more "gentle"
on the forest floor. Because of their design, forwarders can not
be used on steep slopes.
By following best management
practices, logging crews can move logs as needed in a forest and
minimize erosion. Skidding across waterways is necessary, but
should be done in a way that minimizes stream damage, including
streams that are often dry. Beyond erosion, log skidders should
avoid damaging standing trees, except those designated as bumper
Log skidding best
about sensitive areas into the work site.
for a timber harvest, wetlands, streams, and gullies should be
noted on a map. Take this map and other documents to the timber
harvest site to identify areas that should be avoided due to potential
soil erosion problems. Keep the planning process consistent with
the actual forest work.
existing trails if they are suitable.
Try to find existing trails and minor roads that can be used for
skidding. Use these access lanes to reduce skidding distances.
If a route with less environmental impact can be identified, close
down old roads and skid trails permanently. Skid trails should
occupy less than 8% of the area of the harvest.
In some cases when
weather conditions permit, a temporary steep skid road is necessary
to reduce the area of woods impacted. These should be stabilized
immediately after completing the skid work in that area.
Flag or mark skid
trails before skidding work begins.
If older trails are not suitable (poorly constructed, wrong location)
or new trails are needed, avoid the temptation to drive a skidder
or bulldozer right into the woods without planning the route.
Walk across the slope and mark the skid trail with surveyor's
flagging. Change the color or pattern of flagging to designate
main and side trails. Do not use paint, as it may be necessary
to remove the markings if a different route becomes available.
Once planned skid trails are built, stay on them.
cross-slope and use winches on steep slopes or gullies.
To prevent soil erosion, it is almost always better to skid logs
across a slope, rather than driving up or down. The skidder operator
should make sure the tail end of the logs does not slide downward,
damaging other trees. Of course, there are many times when the
timber is either upslope or downslope from the main skid trail.
In these cases, plan to use a combination of directional felling
and winches to move the logs. A bulldozer may be needed to create
a more level trail across a hillside, sloped inward to control
water runoff. With some planning, extra work and the problem of
forest erosion are avoided.
Break up long, straight
Skid trails should have small turns and bends. These turnouts
prevent rain or snow melt water from gathering momentum and eroding
the trail. Some skidder operators have used the skidder wheels
to create effective, temporary cross-ditches on skid roads.
Protect dry stream
beds and small rivulets.
Before crossing over shallow, dry stream channels, temporarily
place waste logs or slash in a protective layer across the channel.
Use this crossing as necessary to prevent damaging the existing
course of the stream. Tires should not make ruts through these
If a wet swale is
crossed, use pole timber or a rubber mat to create a more durable
on dry or frozen ground.
When soil is fully frozen or dry enough to support skidding equipment
without rutting, it is good for skidding. During a "real
winter," many intermittent stream channels are solid enough
to be crossed without eroding. Watch for and avoid springs and
seeps that remain soft even in the coldest or driest weather.
A heavy rain or warm winter day can soften forest soils quickly,
especially around otherwise dry stream channels. Shift operations
to more stable areas or focus logging labor on preparation, safety
training, landowner meetings, and machinery maintenance, all of
which reduce lost time.
Make sure water
running on skid trails does not wash directly into streams.
Just before crossing a stream, make a turn that will cause water
flowing on the skid trail to spread out into the forest, not run
right into a stream. Maintain or install filter strips near stream
courses to trap sediment before it enters the water.
low value trees and stumps as bumpers.
When flagging the skid trail route, designate some low-value trees
as "bumper trees." These are used to intentionally pivot
long logs around a bend without harming more valuable trees.
forecasts and prepare trails for heavy rain by constructing temporary
water bars and turnouts.
When skidding is
completed, inspect the skid trails to make sure water is controlled
and the soil is stabilized.
Look for long runs
to be broken up, steep trails that need water bars, and trails
near streams that should be seeded and mulched.
post-harvest best management practices. . .