Erosion control and forest roads
Build forest roads properly
2. Good construction reduces erosion significantly
3. Make sure roads and skid trails are built
to move small amounts of water short distances
4. Properly built roads need not be expensive.
This web article details the ways
in which loggers and forest owners should prepare and maintain
Forest roads provide the most important
means of accessing forests for timber harvesting, recreation,
and hiking. Unfortunately, forest roads cause more erosion than
any other aspect of logging. When sediment washes away from timber
harvesting operations, it usually starts from erosion along poorly
built forest roads.
though forest roads are important for harvesting timber, reforestation,
recreation, and forestry projects, they should be placed only
where necessary. Avoid building new roads in forests if it is
basic problem of forest roads is that they create a hard, compact
surface within woodlands. Forest soils are naturally permeable
and sponge-like. Forest roads, on the other hand, are much more
impervious, causing water from rain and show melt to run across
the surface, rather than soaking in. Uncontrolled surface runoff
washes away thousands of tons of soil over time. Eroded soil cannot
be replaced without a great deal of expensive and time-consuming
effort. If the surface water is controlled, forest soil remains
in place, providing a good foundation for future forest growth.
types of forest roads:
Temporary roads - These are the most common type
of forest road. They are designed and constructed for short-term
use during a specific project such as timber harvesting.
These roads are used only when the ground is frozen or firm.
When the project is done, the temporary road is closed,
all stream crossing structures are removed, and the road
is naturally or artificially revegetated.
Permanent seasonal roads - These are maintained as
part of the permanent road system but are designed for use
only when the ground is frozen or firm.
Permanent all-season forest roads - These roads usually
have gravel surfaces and are designed for year-round use.
However, there may be some restrictions on use at various
times of the year.
Wisconsin's Forestry Best Management Practices for Water
Quality (1995) Publication number FR093.
road best management practices
After a walk over the land, and after reviewing maps, aerial photographs,
and soil surveys, forest owners should have plenty of information
to find and mark existing forest roads. These roads often provide
the best access to a timber harvest site. If so, inspect the grade
and slope of the road so that they move small amounts of water
short distances. Technicians from the county Soil and Water Conservation
District office can help you with technical information and on-site
an existing road is unsuitable for use (poorly constructed, wrong
location), first make sure the old road is stabilized and will
not create a future erosion hazard. Use the information gathered
about sensitive areas and slopes to design and locate a new forest
accessing a harvest area through adjacent land to avoid steep
slopes or stream crossings. If a neighbor's property is involved
somehow, get written, dated permission from the neighbor allowing
the logger to move their equipment accordingly.
Plan routes for new roads
New forest roads should be built in as few places as possible.
Minimize the length and width of the road to fit the equipment
being used on-site. Planning can reduce skid road area by 40%
compared to unplanned skid roads. Technicians from the county
Soil and Water Conservation District office can help you with
technical information about forest road construction and on-site
Match the road to
the type of equipment in use.
Refer to these guidelines for choosing what kind of road will
||20% slope maximum
a topographic map, count the number of contour intervals crossed
by a potential forest road. The fewer contour line crossings are
to use for forest road routes
||Dip in the ridgeline
good for crossing over ridge
||Flat portion of
hillside - good for switchbacks, intersections, and landings
|Start / end
||Should be identified
||Keep road clearly
on the proper side of a boundary
|- - - - - - - - - - - - - - - - - - - - -
- - - - - - - - - - - - - - - - - - -
to avoid with forest road routes
cross directly at narrow points; leave a buffer zone between
road and stream
||Cross above or
||Avoid or use switchbacks
Avoid streams, wetlands,
steep areas, and ponds with new roads. If the road has to run
close to a stream or other surface water, plan on maintaining
a filter strip, 10 - 40 feet wide. This filter strip will capture
sediment before it runs into the water.
New roads should follow
gentle slopes. On steeper hillsides, a series
of planned switchbacks will help avoid long, straight runs.
On steep slopes, consider constructing
one main skid road with lots of erosion control, joined by several
gently sloping skid roads.
See pages 6
- 15 in Best Management Practices During Timber Harvesting
See pages 18 - 33 of the New York Forestry Best Management
Practices Field Guide for forest road construction guidelines.
water control features within the roadway
are many types of water control features for forest roads (and
A broad based dip is a wide depression in the road designed to
divert water off a sloping roadway. It is broad enough to accommodate
hauling equipment easily, yet move water off the road to disperse
in the forest. They are constructed as the forest roadway is being
built, not dug in afterwards. Cull logs can be embedded in the
mound, perpendicular to the roadway, reinforcing the berm.
broad based dip should be placed on forest roads with long, continuous
slopes. The idea is to collect water running down or near the
road and redirect it off the road, to soil where it will slowly
pipe culvert is a permanent conduit for water that must travel
under a forest road, rather than over. It collects water from
small streams, intermittent waterways, and roadside ditches and
drains it on the downhill side. Although they can be expensive
to install, they are very effective in controlling erosion. The
decision to place one under a new road should be based on expected
traffic, and how many acres are being drained. Make sure the sides
of the culvert are compacted. During
heavy rains, a culvert will make the difference between a stable
or washed-out road.
41 in the NYS Best Management
Practices Field Guide lists culvert size recommendations.
a forest road needs surface drainage, an open-topped culvert provides
good water control at low cost. These stabilized "mini-ditches"
cross the road, but are narrow enough to allow vehicles to cross
over. When built, they should be angled down slope, not straight
across the road. Because they are shallow and unprotected, they
need to be cleaned out periodically to keep water flowing through,
belting, attached to and reinforced by timbers, can help divert
water off a gently sloping forest road. Like open-top culverts,
they are angled downslope so water can move off the road quickly.
Rubber deflectors allow equipment to pass over without interference.
These structures work better on forest roads that are not maintained
and have a low volume of traffic. The area receiving water from
a rubber deflector should be stabilized with cobblestone to prevent
erosion at the lower tip of the deflector.
ditches / Turnouts / Turn ups
Smaller forest roads and skid trails can be stabilized by redirecting
water toward a vegetated area, rather than down the track of a
forest road. With a combination of easily- installed ditches,
turnouts, and turn-ups, a forest road controls water flow and
prevents erosion. In a sense, the forest road appears to "wiggle"
through the woods, shedding water at each small slope and turn.
turn-out directs the water off the side of the skid road, whereas
a sloping turn up sheds water at its base.
Rolling dips are broad, angled portions of a forest road that
shed water off to the side, rather than down the length of the
road. With rolling dips, a forest road appears to pitch gently
from side to side, while maintaining a straight course through
the woods. This technique is also called outsloping.
Use the proper cross-section
The location and position of the road will help determine which
cross section will be most effective in controlling erosion. Grade
the road to create good drainage. Direct water that drains to
flow without force off to more stable ground. The insloped road
should include a catch ditch and a culvert designed to move the
water back underneath the road.
when weather conditions decline
Shut down log skidding and hauling when the soil is saturated
and unable to support the equipment. In a good logging job, skidders
and bulldozers should be supported by soil, not slogging through
it. When forest soils cannot support the equipment, focus the
logging efforts on machinery maintenance, planning, and preparation.
Logging crews throughout New York lose thousands of hours of work
time trying to pull out stuck equipment and repairing deep ruts.
There is a point where skidding costs exceed site damage and are
not worthwhile. In some cases, logging crews have been barred
from future work in forests due to poor judgment regarding forest
Drawings are from Wisconsin Department
of Natural Resources (1995) Wisconsin's Forestry Best Management
Practices for Water Quality.
Publication number FR093.