According to the Student Conservation Association in their Lightly on the Land, trails, the paths that take us up to our views, down to our valleys, and along our rivers, have been around a long, long time: “Trails are among the earliest marks left by humans on the face of the Earth.” Simply put, trails were around when wooly mammoths were around and trails will be around when you are not. And though trail construction techniques have advanced, no trail builder can reinvent the wheel.
However, today’s trails are not about traveling from point A to point B. They’re about exercising, experiencing, and enjoying. What Northeasterners thus want are high-quality sustainable trails, and it is high time we give it to them (in the West and South they already have nice trails – it’s us Northeasterners who feel left out). To be enjoyable and sustainable a trail need only follow four rules.
1. Average trail grade should not exceed ten percent.
2. Trail grade should not exceed half the slope.
3. The trail should drain naturally – no waterbars.
4. The trail should include an outslope.
Do these four and you get these four:
1. Trails will not erode – they’ll be sustainable.
2. Maintenance costs will be minimal.
3. Users will see trails as destinations, not just destinations as destinations.
4. Trails will provide users physical and psychological satisfaction.
Now here’s how to do it.
Average trail grade should not exceed ten percent
Too many Northeast trails run straight up and down hills, which enables runoff to channel and gain momentum. The faster runoff moves (and the more runoff you have), the faster trails erode. With a mellow grade, water merely crawls down mountains.
To lay out your grade, don’t guess the steepness. Always use a high-quality clinometer (a handheld device that measures grade and slope). Suunto makes a nice one for $150. Take good care of it. Don’t let anyone borrow it. A basic formal employed to measure grade otherwise is this: vertical rise ÷ linear run = grade. To give you a feel for what ten percent is, the steepest railroad grades in the U.S. are two percent. And most beginner mountain bikers can ascend a ten percent grade without trouble.
Trail grade should not exceed half the slope
Trail users think “grade” and “slope” are synonymous. Not so. Grade is the linear angle of the trail (how steep the trail is). Slope is the angle of the hill the trail is built on (how steep the side hill is). This means that if you build on a four percent slope, your grade can’t exceed two percent. If you build on a sixteen percent slope, your grade can’t exceed eight percent. And if you build on a thirty percent slope, your grade can be up to fifteen percent. Oh, I got you on that last one – grade should not exceed ten percent, no matter how steep the slope.
The trail should drain naturally – no waterbars
To those who design sustainable trails, waterbars are “the W word,” nastier and dirtier than “the F word.” Why? Because waterbars are ineffective. What waterbars really collect and then move off the trail is not water but the trail itself. Proof of this? Waterbars need to be cleaned out annually because they are packed to their brims with mineral soil, which used to be the trail.
Trail builders prefer the “RGD” – the rolling grade dip. A rolling grade dip is where the trail climbs a little, then descends a little, then climbs a little, and so forth. This divides the trail into miniature watersheds where little water can collect. Rolling grade dips work with the land, not against it.
The trail should include an outslope
Okay, we have our mellow grade (which doesn’t exceed half the slope) and our rolling grade dips. That’s the cake. Now for the icing: a ten percent outslope. Outslope is the outward tilt of the trail tread that is sloped towards the downhill side of the trail. A good outslope serves as a backup to the rolling grade dip.
Just like how you should not guess the grade, you should not guess the outslope. The SmartTool digital level is a great device, retailing for $150. It measures in degrees and percentages and is durable and easy to use. Once you use this tool for a few weeks you’ll get the feel of a ten percent outslope. Basically, if you walk on your new trail and your ankles are working hard to keep you upright, your outslope is too aggressive.
While Northeast-design trail crews are feverishly cleaning out waterbars and wondering why their jobs are so hard, sustainable-design trail crews are sitting back with their feet kicked up, enjoying trails that need little maintenance. And experts are conscious of this waste and non-waste of time, the International Mountain Bike Association writing that “Land managers don’t have the time, money, or manpower to constantly rebuild each trail under their jurisdiction…”
The time has come to build sustainable Northeast trails that build great experiences while saving time, effort, and money. And now that we know how to do it, the real question is, why not do it?
– Erik Schlimmer designs sustainable trails for federal, state, and private agencies. More on his adventures and credentials can be found at www.erikschlimmer.com.