This document is reproduced with permission from California State Parks
A Cursory Look at Trail Maintenance
INTRODUCTIONThis document focuses on wilderness trails only and is
intended to be used as a reference by trail maintenance crews. If you have
questions about the contents, please do not hesitate to contact Clay Phillips at
the Southern Service Center of California State Parks at (619) 220-5303.
Trail construction and maintenance is an inexact science with many variables.
Much depends on the location of the trail, the soil, the climate, and the types
of uses. However, there are certain general guidelines which, if adhered to,
will prevent most trail deterioration and minimize maintenance costs.
Trail ProblemsTrail users may not be able to articulate what a
"perfect" trail looks like, but almost everyone can list the characteristics of
a "bad" trail:
- Deep Trenching - The trail is sunken such that hikers feel like
they're walking in the bottom half of a pipe and equestrians drag their spurs.
- Widening - The trail has widened from a single or double track to
an unsightly wilderness "freeway" of multiple parallel tracks, all trenched to
a different degree.
- Short Cuts - Knowing that the shortest distance between two points
is a straight line, users create a web of trails, most of which are steep and
- Tripping Hazards - Regular use and erosion ultimately expose tree
roots and rocks.
- Steepness - If a trail is too steep over a long distance one of two
things will happen: either people won't use it, or users will not enjoy their
- Impact to Natural / Cultural Resources - Erosive trails and
multiple trails compound the impact that trails have on rare plants and on
CausesAll of these problems can be tied to one or more of the following
- Water is the foremost cause of trail problems. The movement of
water causes erosion and deep trenches. It also exposes tripping hazards.
- Poor Initial Trail Design can rarely be overcome, even by regular
- Inadequate or Inappropriate Maintenance wastes valuable crew time
and can sometimes increase trail problems.
DESIGNING FOR TRAIL MAINTENANCEUltimately, the most influential
component of trail maintenance is the original trail design / alignment. A
well-designed trail will be easier to maintain, will deteriorate more slowly and
will be more pleasant to use. On the other hand, a poorly-designed trail is
difficult to maintain, deteriorates quickly and, once you lose it, there's not
much that can be done to restore it. In addition, a poorly designed trail will
always be less pleasant to hike or ride.
Elements of a Well-Designed TrailThere are many factors which go into a
well designed trail; here we will only look at the elements required from a
Generally, the linear gradient of a trail should be
less than 10%. The term "gradient" refers to the ratio of the rise over the
run. In other words, an elevation gain of 2 feet in 20 horizontal feet
represents a 10% gradient. Ten
percent is a good standard, but circumstance may warrant a greater or lesser
In highly erosive, sandy soils, a 5% slope may be excessive. Granitic soils
are more forgiving and can allow long sections of trail to be constructed at
13 to 15%. It is best to look at existing trail conditions and measure
gradients to determine what maximum gradient works best in each unique
condition. However, it should be noted that trails less than 10% are far more
comfortable to hike and ride. The soils may allow for a trail that exceeds
10%, but the users might not!
- Relationship to Existing Contours
In map jargon, a contour is a
line of points that are at the same elevation. If you walk precisely parallel
to a contour, you are walking at a level (0%) grade. If you walk perpendicular
to a contour, you are walking either straight uphill or straight downhill. A
well-designed trail is laid out to traverse a hillside, closer to parallel
than perpendicular to the contours.
The figure below shows two proposed trail routes to the top of the hill.
Although Trail A stays within a gradient of 10%, it is the poorer route
because it travels perpendicular to the contours. When a trail runs
perpendicular to the contours, water runs down the middle of the trail,
causing trenching, even at a 10% gradient. The only way to get water off the
trail is for the route to traverse the natural slope (Trail B), because
then there is always a lower side of the trail. When there is a lower side of
the trail, it becomes a simple matter to redirect water across and off the
trail, rather than allowing it to cut a channel down the trail's centerline.
A well-designed trail should be constructed to have a
3% to 4% cross-slope to get the water off the trail as soon as possible. This
explains why it is difficult to construct an effective trail in a flat meadow.
You can not merely cut out sod and call it a finished trail. It will always be
easiest to construct an outsloped trail if the original trail alignment
traverses the natural slope as in Trail B, above.
- Avoid Switchbacks
A "switchback" is any place where the
alignment of a trail traverses a slope in one direction and then abruptly
"switches back" toward the opposite direction. Switchbacks are often used to
run a trail up a steep slope in a constrained location. Although switchbacks
are often the only solution to the problems of rock outcrops and steep slopes,
they should be avoided where possible. Unless they are perfectly designed and
constructed, switchbacks present an irresistible temptation to shortcut the
trail and cause erosion over a web of indiscriminately created volunteer
KEY ELEMENTS OF TRAIL MAINTENANCEThe first step of trail maintenance is
to inspect the trail. When erosion problems are evident, the principle questions
to ask are, "Where is the water going and how can I get it off?"
The following elements represent the primary "tools" to be used in the
maintenance of trails. They are generally listed in priority order, but each has
its own special application and purpose. Clearly, though, the first 3
(Maintaining the Outslope, Install and Maintain Water Bars, and Maintaining
Drainage Dips) are far and away the most important.
Maintaining the OutslopeThis is the first order of business in
trail maintenance. It is the simplest, but most labor intensive trail
Normal trail use will build up a berm along the outside (downhill) edge of
the trail (Stage 2 of figure 4). If allowed to continue, the berm will grow and
prevent water from flowing off the trail, causing gullying down the centerline
of the trail (Stage 3). If this centerline gullying is allowed to continue
unchecked, the trail will trench deeper and deeper until it is both unusable and
unredeemable (Stage 4).
outslope is maintained at Stage 2 by simply pulling the small 4" - 5" berm back
into the trail tread. This unglamorous work must be performed again and again by
trail crews, but in many cases, it the outslope is restored on a regular basis,
little or no maintenance is needed of any other kind. However, some use patterns
(extensive equestrian use), soil conditions (sandy) and climate conditions (high
precipitation) combine to minimize the effectiveness of this maintenance tool;
it just has to be done too often to make it worthwhile.
Once a trail has reached Stage 3, the berm is too large and overgrown with
vegetation to be removed; the outslope cannot be restored and other maintenance
approaches must be employed. When a trail deteriorates to Stage 4, the trail is
a lost cause, and the best solution is trail abandonment and relocation.
Install and Maintain Water BarsWater bars divert water off a trail
at controlled points along the trail. They can be incorporated in the original
construction of a trail, or they can be installed later as a maintenance
measure. Done well, a series of water bars can effectively eliminate erosion and
stabilize a trail for years. Done poorly, water bars can accentuate trail
erosion and become dangerous tripping hazards.
The most permanent water bars are made from native rock obtained on-site.
When rock of a suitable size is not available, water bars can be made from 4 x 6
redwood timber, or native logs. Peeler logs or other landscaping products should
not be used because their appearance is foreign to a natural environment.
Bicyclists prefer a new product made of black rubber that diverts water, but is
flexible enough to allow cyclists to easily cross. However, this too, may be
inappropriate for a natural environment.
There are many options about the proper installation of water bars. Three
trail handbooks will promote three different approaches. Well, here is one more.
The elements of a properly installed water bar are:
Water bars need regular maintenance.
The excess soil and debris that build up at the down slope end of the water bar
needs to be periodically graded out to assure that water flows off the trail.
Without regular unplugging, a water bar is useless.
- Set the water bar at a 60 degree angle across the trail. A water
bar set perpendicular (90 degrees) across the trail will not divert the water
off. A water bar set 30 degrees across the trail can be awkward to hike or
- Extend the water bar such that water is carried completely off the
trail to a steep side slope. Otherwise, the water flow will bypass the
water bar and erosion will occur.
- Provide rock at the down slope end of the water bar to dissipate the
energy of the flowing water, thereby minimizing erosion.
- The top of the water bar should be nearly flush with the trail
tread to minimize tripping hazards. On first consideration, it may not
make sense to make the top of the bar flush with the tread because there would
be nothing to "catch" and divert the water. However, we are not concerned
about diverting all water flowing down a trail, only that amount of
water than causes erosion. With the bar flush, its effectiveness only kicks in
when there is enough water to erode away a lip on the uphill side of the water
bar, which then allows the bar to divert the water flow.
- The boulders used for rock water bars must be huge, otherwise, they
will be kicked out of place by a horse. The rocks should overlap like shingles
on a roof to prevent water from flowing between rocks and eroding away the
integrity of the water bar. In addition, long boulders with one flat side work
best to prevent tripping hazards.
Maintaining Drainage DipsA drainage dip is built into the original
trail alignment and is a change in gradient (a "dip" in the trail) that
dissipates and diverts water flow (it's like a built-in water bar). Like a water
bar, it only remains an effective means of erosion prevention as long as regular
maintenance keeps it unplugged.
PruningPruning vegetation is an essential and regular part of trail
maintenance, especially in brushy chaparral areas. Multi-use trails should have
10' vertical and 8' horizontal clearance (though there will be exceptions for
the sake of protecting a tree or skirting around a large boulder).
Too often, trail pruning is accomplished in the most expeditious manner
possible -- a branch intrudes within the walking/riding space of the trail and
is quickly lopped-off so that it doesn't intrude and the debris is indiscriminately
tossed aside. However, our goal in trail maintenance is to
maintain a trail in as natural appearance as possible. A quick pruning
job deals only with the function of trail maintenance, not the aesthetics.
There are 6 elements of acceptable pruning in the State Park System. Each of
these elements makes pruning a more tedious maintenance task, but results with a
trail that is compatible with the natural environment.
- Do not toss debris! Branches that are randomly discarded usually
end up hanging in adjacent shrubs or trees. These dead branches are both
unsightly and create a fire hazard.
- Place debris out of view. This element requires the extra effort of
dragging branches under and around shrubs.
- Place the butt (cut) end away from the trail. This will help
disguise the debris.
- Each cut branch should be touching the ground to promote
decomposition. This means that brush piles are not appropriate.
- Pruning should be done sensitively so that the trail appears
natural and not as if a chain saw just blasted through. Trail users should
not be aware that any maintenance work has recently been done.
- Prune to the collar of any branch stem for the health of the shrub
and a more natural looking result. At the base of any branch there is a wide
section that contains a plant's natural healing agents. Any pruning performed
away from this collar will expose the plant to a greater risk of infection. A
cut at the collar will naturally heal. For large branches over 2" in diameter,
cut from the bottom, then cut down from the top. This prevents tearing of the
bark, reducing infection.
Signing / MappingAdequate signing and mapping keeps trail users on
the trail. Uncertainty about which trail is which will lead to new trails being
created by trail users. These new trails will become maintenance headaches and
will ultimately need to be abolished.
Check DamsCheck dams are a popular, though generally ineffective,
instrument of trail maintenance. A wood timber is placed 90 degrees across a
trail. In theory, the check dam is intended to slow the velocity of water
flowing down the trail, thereby reducing erosion. In reality, nearly all check
dams only halt erosion in the 2 to 3 feet immediately behind the check dam, but
accelerate erosion immediately below and beside the dam. This is because they
never take the water off the trail, they only slow it down momentarily. For
check dams to be truly useful in stopping erosion, they need to be spaced 3 feet
apart, and this effectively makes a stairway out of the trail.
Check dams should not be used in trail maintenance. However, they may have
limited application in restoring abandoned trail alignments to natural
Import Fill MaterialA deeply trenched trail can be restored by
importing dirt or decomposed granite, compacting it, and recreating a
well-drained outsloped trail. However, in most situations, this approach is
usually both cost prohibitive and far too labor intensive.
TRAIL REROUTINGTrail rerouting is beyond the responsibilities of a
trail maintenance crew. New trail alignments must be flagged by experienced park
staff and then reviewed by resource specialists for compliance with the
California Environmental Quality Act. Trail maintenance crews can provide
valuable assistance by alerting park staff to those trail routes that may need
to be rerouted.
There are two measurements that dictate that a trail relocation is needed:
- When the maintenance crew is dealing with a poorly designed trail that has
deteriorated to the extent that remedial measures will not work or will
constantly need repair or replacement, AND
- A significantly better route is available.
telltale signs of a trail that needs to be relocated are: deep trenching and a
gradient exceeding 20% over about 100 feet of trail.
REFERENCE MATERIALThis document represents a cursory look at the
basic aspects of trail maintenance and only briefly touches on trail
construction techniques. There are many valuable references that dive into much
greater detail; a few are listed below. Each of them can be obtained by
contacting the sponsoring agency.
NPS TRAILS MANAGEMENT HANDBOOK, United States Department of the
Interior, National Park Service, Denver Service Center, 1983 (A small, but
comprehensive, pocket manual on trails construction and maintenance.)
Trails Coordinator, National Parks Service
P.O. Box 25287, 655 Parfet
Street, Denver, CO 80255
A TRAIL MANUAL, East Bay Regional Park District, Oakland CA. 1976
GUIDE FOR MOUNTAIN TRAIL DEVELOPMENT, United States Department of
Agriculture, Forest Service, 1984
Forest Service - USDA
Engineering Staff - Washington Office, Attn:
P.O. Box 2417, Washington, D.C. 20013
TRAIL DESIGN, CONSTRUCTION, AND MAINTENANCE, Appalachian Trail
Conference, Harper's Ferry, 1981
Appalachian Trail Conference
P.O. Box 236, Harpers Ferry, WV
TRAILS MANUAL, Charles Vogel, 1968
Equestrian Trails, Inc.
10723 Riverside Drive, North Hollywood,