2006 World Summit Resource: Building Sustainable Trails
Speakers: Rich Edwards, IMBA; Woody Keen, Trail Dynamics; Tony Boone, Arrowhead Trails Facilitators: Kristin Butcher and Ryan Schutz, IMBA
The speakers, all master trailbuilders, began by offering three goals they all strive for when designing and building trails: 1) limit environmental impacts; 2) keep maintenance requirements to a minimum; 3) avoid user conflicts.
They continued by offering a checklist for building sustainable contour trails. A contour trail is a path that gently traverses a hill or sideslope. It's characterized by a gentle grade, undulations called grade reversals, and a tread that usually tilts or outslopes slightly toward the outer edge. These features minimize tread erosion by allowing water to drain in a gentle, non-erosive manner called sheet flow. When water drains in thin, dispersed sheets, dirt stays where it belongs - on the trail.
Contour Trail Tips:
- Do everything you can to keep the water off the tread, and users on it
- Build on the contour and use frequent grade reversals - surf the hillside
- Follow the half-rule: A trail's grade shouldn't exceed half the grade of the sideslope
- Maximum grade should be 15 percent (except for natural or built rock structures)
- Average grade should stay under 10 percent (with grade reversals)
- Route trails to positive control points (viewpoints, water, other attractions)
- Use bench-cut construction, and excavate soil from the hillside
- For reroutes, reclaim old trail thoroughly - the visual corridor as well as the trail tread
- For highly technical trails where grade will sometimes exceed 15 percent, use natural rock, rock armoring or other rock features to add challenge and improve sustainability.
- Avoid the Fall Line
Fall-line trails usually follow the shortest route down a hill - the same path that water flows. The problem with fall-line trails is that they focus water down their length. The speeding water strips the trail of soil, exposing roots, creating gullies, and scarring the environment.
- Avoid Flat Areas
Flat terrain lures many trailbuilders with the initial ease of trail construction. However, if a trail is not located on a slope, there is the potential for the trail to become a collection basin for water. The trail tread must always be slightly higher than the ground on at least one side of it so that water can drain properly.
- The Half Rule
- The 10-Percent Average Guideline
- Maximum Sustainable Grade
- Grade Reversals