How Are Wilderness Trails Built in the 21st Century?
“Of trail making there are three stages: There is dreaming of the trail, there is prospecting the trail, there is making the trail. Of the first one can say nothing – dreams are fragile, intangible. Prospecting the trail – there lies perhaps the greatest joys of trail work. Making trails is the more plodding work; yet it has reliefs and pleasures of its own.” Nathaniel Goodrich, New England Trail Council, 1917
“Trails . . .We Dig ’em” has been the tag line for the Cumberland Trails Conference for a long time. It is sort of play on words in that, we like trails, but also literally; we build trails.
Trail building has come a long way since the early days of the Appalachian Trail and loop trails in state or national parks. The AT and the Pacific Crest trails are among the earliest examples of organized efforts to create long distance trails that provide access to wilderness areas for hikers.
Fortunately, the science and art of trail building has evolved and changed over the years. In the 21st century trail building organizations and government agencies strive to build “sustainable trails.” Sustainability basically means that the trail is built to withstand the destructive forces of water and user traffic with a minimum of maintenance.
Much of the research and testing of current trail construction techniques can be traced to Mike Riter, founder of Trail Design Specialists. During a twenty plus year career with the State of Georgia he was able to put his training as a hydrologist to work and develop rules for trail construction based on a scientific understanding of how water behaves. Virtually any manual or article on trail construction published since 1995 highlights rules, formulas and guidelines originally developed by Mr. Riter.
The Cumberland Trails Conference has been building trail since before its official formation in 1996. As a contract agency, charged with building trail that becomes part of the 300 mile Cumberland Trail State Scenic Trail in Tennessee, the
CTC takes very seriously the quality of trail construction. Although seasonal trail crews do much of the construction, a huge amount is done by volunteers. Some volunteers have racked up well over 1,000 hours digging trail. Hundreds of others are approaching 500 hours. And over a thousand have given 100 hours or more to the trail.
In addition to our paid crew, volunteer trail builders are trained and work under the immediate supervision of crew leaders – locally known as WagonMasters. WagonMasters are skilled builders who can also teach on the job and organize the efforts of their crews to make the most of the abilities each volunteer brings to the job.
Periodically, CTC offers WagonMaster leadership training courses for volunteers who want to become crew leaders. Classes are open to all volunteers but a few days of trail building experience is recommended. Check the News section for class dates and locations.
Since 2012 the State of Tennessee has sent a dozen Park Rangers to trail building school, earning the rating of Certified Master Trail Builder. The same year individual CTC volunteers began taking the nationally recognized course and paying for it on their own. By 2015, ten CTC WagonMasters were Certified Master Trail Builders.
For the benefit of our new volunteers, we have put together an illustrated outline explaining some of the tools we use and some crucial trail building concepts. Many of the photographs in this section feature college students who participate in our month long BreakAway program. Details can be found elsewhere on this web side.
Tools . . . . . .
Frequently when we talk to civic groups, hiking clubs and government agencies the question of chain saws come up. For some reason when the novice hears “trail building” they think chain saws. The short answer is, NO, we don’t go into the woods and cut down trees to build a trail. Chain saws are used mostly to clear downed trees that block the alignment of the trail.
Most trail building tools are adapted from wilderness fire fighting tools. The four principal tools are:
The Mattock- The basic trail building tool has its origins in the Bronze Age and Ancient Greece. The word mattock begins to appear
in the early 17th century. Mattocks come in two styles, the cutter and the pick. Pick Mattocks are useful in rocky soils where the pointed end can penetrate between rocks and loosen the ground. Cutter mattocks are the tool of choice for initial removal of duff and the root zone above usable mineral soil. These terms covered below.
McLeod- A wilderness fire fighting tool developed by Malcolm McLeod in the early part of the 20th century. McLeod was a Forest Service employee and created the tool by welding a long tine rake with a wide hoe blade. The blade is usually sharpened. As a fire fighting tool it is used to pull up roots and quickly dig fire lanes. The head is removable so fire fighters can carry the tool in a backpack and keep their hands free. As a trail building tool it is invaluable for removing roots, moving soil along the trail and for final grooming of the trail tread.
Fire Rake – the volunteer student in the foreground is using a fire rake. Behind her is a student using a McLeod. Both tools are used for removing leaf litter, organic matter (known as Duff) and the root layer from the ground.
Later in the process both tools are used for final grading and grooming of the trail tread.
Pulaski- The Pulaski is a versatile double headed cutting tool. It is used to cut roots and cut out small bushes and saplings. Pulaski’s are kept very sharp and generally are the only tool with a leather head covering for safety.
Here volunteer students remove a sapling from the trail alignment with a Pulaski in a process known as “Grubbing.” Saplings and small trees in the trail corridor are first cut off about 40 inches from the ground. The resulting stub provides leverage needed to pull out the tree with the roots intact. Leaving the roots behind invites the tree to grow again in the trail and leaves a tripping hazard.
The tool is named for it’s inventor, Edward Pulaski, a Forest Service Supervisor in Idaho at the beginning of the 20th century. He took an axe and welded a narrow cutting blade at right angles on the opposite side. The tool can be used for cutting trees or quickly removing burning roots of small trees and bushes. Pulaski is well known for protecting his fire crew during the disastrous Wallace fire in 1910 by taking them into an abandoned mine. Of 45 men, only five did not make it. The site is now a museum.
Loppers- The same long handled pruners used to cut small branches are also used to cut roots up to two inches out of the trail tread.
Hand Clippers- Common garden clippers used to cut small roots and branches. Many volunteers bring their own clippers and carry them in a belt sheath for safety and convenience.
Folding Saws- Small trimming saws generally with a nine inch blade. Used to trim branches that overhang the trail or cut larger roots out of the trail.
Rouge Hoe and Grubbing Hoe- In CTC parlance the photo here is of a Rouge Hoe. Except Rouge refers to a manufacturing company that makes a
variety of tools. In 2015 CTC added a similar tool with four wide prongs, or teeth, on one side, also made by Rouge Manufacturing.
We call it a “Grubbing Hoe” because it is an efficient tool for removing or “grubbing” out tree roots in the trail corridor. The version we use is only 5.5 inches wide, so it is excellent for clearing duff around rocks as well.
Five Inch Grubbing Hoe and leaf litter from around large rocks and boulders.
The Behavior of Water . . . .
” No factor in trail construction is more important than proper drainage, and many sections of good trail are damaged and destroyed by erosion which could have been prevented.” —CIVILIAN CONSERVATION CORPS, Construction of Trails Handbook, 1937
The above quote from 80 years ago speaks to modern trail building techniques. A sustainable trail means it is resistant to the impact of water, hikers and to a lesser extent, wind.
Unfortunately it took more than 60 years before the study of water run off was converted into sound guidelines for trail construction. A full discussion of dealing with water in trail design is not the intent of this section. But a little insight to how water behaves relative to a trail helps builders understand why trail is designed a certain way.
Two principal concepts prevail: The Fifty Percent Rule, and the Ten Percent Rule.
Fifty Percent Rule- This rule applies mostly to trail designers but helps explain to builders why a trail was routed to one place and not another. Simply it says; the grade of the trail must not exceed fifty percent of the natural slope it is cut into. For example, if the natural hill side is a 30 percent slope (17 degrees), the grade of the trail must not exceed 15 percent (8.5 degrees). This allows rain water to sheet across the trail rather then turn and run down the trail tread creating an erosion problem. If the trail grade is steeper than half the angle of the natural slope, water will not have the speed to cross the trail. The trail tread itself has an outward angle of about 3 to 5 percent. More on that in the next section.
Trail Terms . . .
Trail Tread- The walking surface of the trail. On the CT, newly finished trail ranges from 3o to 34 inches wide. Properly constructed trail tread slopes from 3 to 5 percent toward the down hill side to allow water to move off the trail without eroding the tread. Note that in trail building Percent is used as a unit of measurement rather that degrees. Percentages give a finer measure of slopes and grades. Thus 45 degrees is 100 percent.
Duff- A US Forest Service term for the leaf liter and organic material on the first few inches of the ground. Sustainable trail can not be built on Duff. The roots and other organic material will break down and create places for water to collect. Roots left behind promoted the growth of plants in the trail tread, increasing maintenance efforts.
Duff Removal with the Zipper Method – Honest trail diggers will admit they hate removing Duff. Yet it is one of the most critical functions of trail building. To make Duff removal a little easier and avoid leaving Duff behind this method is a step in the right direction.
After raking off the loose leaf litter the digger used a mattock to cut a line down the center of the trail. Working in section about six feet long helps make the job more manageable.
Next the digger works to remove the Duff on the DOWNHILL half of the trail first. Instead of slamming the mattock into the ground, the head is skimmed at a shallow angle just under the surface. The idea is to separate the Duff and roots from the mineral soil. In many cases the Duff begins to come up in sheets like a carpet instead of in little chopped up pieces. The Duff is then lifted away and spread into the woods on the downhill side.
Rocks ! A fact of life in trail building. The rules about rocks and Duff handling are simple on the CT. Duff goes DOWNHILL and rocks go UPHILL. Rocks are simply placed on the up hill side of the trail above the back slope – not as a wall – but randomly. Sometimes in small collections near the base of a trees next to the trail. These rocks are valuable inventory for crib walls, armoring or filling in holes left from stump removal. Instead of covering them with Duff below the trail, placing them above the trail keeps them visible and easy to find when needed.
Back to the Duff – Once the digger is satisfied that the downhill side of the trail is free of Duff the process is repeated on the uphill half. The cut and loose Duff is lifted out and again spread into the woods on the DOWNHILL side of the trail alignment. Using this method of downhill half first keeps the Duff on the lower half from being covered when simply starting at the top.
Mineral Soil- Once the Duff is removed along with a the layer of roots under it, soils can be found to make a stable trail tread. The term may vary in different parts of the US, but along the Appalachian Range the workable soil is generally called Mineral Soil.
Full Bench Side Hill Cut – Trail that is cut into the side of a slope in such a way that the tread is fully supported by the existing soil.
Half Bench is a technique that takes the soil from digging out the hillside and uses it to construct the down hill side of the trail. Half Bench construction is discouraged on the CT.
Out Slope- The down hill side of the Trail Tread.
Back Slope- The up hill side of the Trail Tread. Trail builders will refer to “laying back” the slope. As a trail is cut into the side of a hill, the up hill side will be straight up. Leaving the back slope straight up allows water flowing down the hill to cascade like a water fall onto the tread eroding the trail. Over time the uphill side of the trail collapses onto the tread either narrowing the trail to a few inches or washing it out altogether. The process is called “sloughing.”
In general the Back Slope is “laid back” to at least 100 percent (45 degrees). Less if possible. ie: 25 or 30 degrees)
Rock Work- Trail builders either love rock work or hate it. Rock work includes steps, crib walls, armoring, stream crossings, gargoyles and causeways.
Puzzling- Puzzling is the process of fitting flat rocks together as an integral part of the trail tread. It can be used where there are lots of rocks and not enough workable soil. Or it can be used in a high impact area like an approach to a bridge shown here.
Steps- The geology of the Cumberland Plateau lends itself to building steps from locally available stone. Occasionally steps have to be made of pressure treated wood or landscape timbers. The photo at left shows the construction of stairs by overlapping the front of each higher stone 4 to 6 inches on the step below. Steps are always started from the bottom up. Rocks should be at least 5 inches thick and not more than 8 inches. But sometimes you work with whats available.
Modern sustainable trail building seeks to avoid structures on the trail, favoring climbing turns to gain elevation. Sometimes steps are unavoidable. Hikers hate steps. They break the natural stride of the hiker. For this reason the ground on either side of steps becomes worn and smooth from hikers avoiding the steps. These smooth troughs allow water to flow into the trail, damaging the trail below the steps.
To force hikers to use the steps, rocks are placed in random, jagged and upright positions along the edge of the steps. This prevents the development of drainage next to the step. These rock structures are commonly known as Gargoyles.
Cribbing- Like any structure, crib walls are avoided if at all possible. But when required, crib walls can vary from a single line of rocks to walls several feet high. Typically crib walls serve to hold back gravel and mineral soil on the down hill edge of a trail where the slope is too steep to hold naturally. Crib walls are wide at the bottom and lean back slightly toward the trail. Occasionally a crib wall is used when the trail needs to bridge a space between two high spots and the natural dip would be to severe. Building crib wall requires some study, instruction and experience to master.
Armoring- Armoring is defined differently on different trails and in different circumstances. On the Cumberland Trail it refers to placing a line of flat rocks along the down hill edge inside the trail tread, angled into the tread about 15 percent and covering them with 2 to 4 inches of mineral soil. The result is a reinforced trail edge where existing soil conditions are too soft to support foot traffic without sliding away. Armoring is generally done in sections of 6 feet of less.
Flagging Tape and Pin Flags- Several photos in this section show pieces of ribbon tied to trees or short orange flags in the ground. The ribbon flags is made from Surveyors Tape and are just called “flags.” The flags in the ground are called “pin flags.” Tree flags mark the intended route of the trail. The knot in the flag always faces the side where the trail is to go.
Pin Flags are used in a number of ways. When first arriving at a new work section there may be a line of Pin Flags marking the Center Line of the new trail. Once work begins, the Crew Leader will move the flags to the up hill side of the trail marking the top edge of the Back Slope.
It is always a good idea to ask the Crew Leader before digging if the Pin Flags are marking Center Line or the Back Slope.
Changing Elevation . . . .
Climbing Turn- When space and terrain allow, climbing turns are the preferred way of gaining elevation. Numerous guide books prescribe the proper way to build a climbing turn. The diameter of the turn varies according to the purpose of the trail. Multi-use trails may have a radius of around fifty (50) feet. On foot traffic only trails, like the CT, the diameter can be fifteen or twenty feet depending on the slope of the land.
Fortunately, trail alignments on new sections of trail (or realignments) are surveyed and laid out by trained and experienced designers. Volunteer trail builders need only follow the flag line left by the designer. But having a general understanding of climbing turn theory helps the new trail digger understand why the trail is being built in a specific way.
Fifty Percent Rule- This rule applies mostly to trail designers but helps explain to builder what a trail was built in one place and not another. Simply it says that the up grade of the trail must not exceed fifty percent of the natural slope it is cut into. For example, if the natural hill side is a 30 percent slope (17 degrees), the grade of the trail must not exceed 15 percent (8.5 percent). This allows rain water to sheet across the trail rather then turn and run down the trail tread creating an erosion problem.
Switchback- Switchbacks are used to change elevation when the side slope is to steep to create a climbing turn. Proper switchbacks require attention to the ruling percentage of the side slope and percentage of grade for the trail. Like crib wall, building them requires some study, instruction and practice. Poorly built switchbacks can easily wash out leading to maintenance headaches for years to come.
Small Water Crossings . . . .
Step Over- Sometimes called a Rock Hop crossing. Typically used on seasonal drainage. Like all rock crossings the key is to use rocks big enough that they won’t be dislodged by water flow from a heavy rain. The rule of thumb is, if one person can move it, it isn’t big enough. Rocks on both sides need to be at the same level. This allows water to rise evenly on both sides lifting leaves and sticks out of the gap. Uneven placement allows sticks to hang up, holding back debris and clogging the crossing. With a ten inch minimum gap, the volume of water should keep the crossing clear and not interfere with the stride of a hiker.
Big Water Crossings . . .
Wider streams require different solutions. Shallow streams can be crossed using large flat rocks if they are available. Like the Step Over crossing, rocks have to be big enough not to be dislodged during heavy stream flow. The rocks also have to be placed so the tops are all even. As the water rises over the tops of the rocks, it will lift debris out of the gaps and there will be no uneven places for floating sticks to snag. Spacing between rocks varies with local conditions but a gap of 20 to 24 inches is reasonable. Less than that invites constant visits to clear debris.
Bridge construction projects are fun to volunteer on, but the design and engineering is left to professionals.
Further Reading . . . . . .
US Forrest Service / USDOT Trail Handbook – latest edition. CTC tries to give a copy of this to everyone who takes the WagonMaster (Crew Leader) training class:
Virginia Greenways Trail Building handbook:
National Park Service. Chapter 5 on trail structures and drainage design issues. Detailed, well written and a wealth of information:
NPA North Country Trail Scenic Park Construction Manual. Runs from Michigan to Pennsylvania. Part of the Great Eastern Trail. Another excellent reference for trail building challenges.
“How are Wilderness Trails Built in the 21st Century” written by Mark Richie. Photos by the author unless noted.