While not many land parcels have contour lines as visible as those in this photo, contour lines play a key role in trail design. Trails that follow the contour are much more sustainable than trails that go straight up and down the slope.
- From the National Park Service, Rocky Mountain Region, January 1991
IMBA works to create sustainable trails. Two key considerations are proper siting and construction to reduce erosion. Minimal maintenance is important because trails are just one of many facilities that land managers must care for. The less time, labor and money needed for trail maintenance, the more likely trails will remain open for mountain biking and other public use.
Achieving balance between soil protection and recreation is what good trail design and construction are all about. A good trail is both sustainable and fun. Trails also must be appealing enough to keep users from wandering off and increasing the risk of erosion.
Erosion is the natural process of wearing and moving rock and soil by wind and water. Trail erosion can be accelerated by the combination of users, water and gravity.
All trail users loosen soil, especially on steeper grades where they resist gravity. Water compounds the process if it's allowed to channel or "focus" down the trail. Water takes loose soil with it, cutting deeper into the tread (clear path for travel) each time it flows.
The goal is to encourage sheet flow - a dispersed flow of water down a hillside. When water is allowed to focus, it can do more damage than any trail user. Erosion is minimized when trails are designed to make water sheet rather than focus.
While not many land parcels have contour lines as visible as those in this photo, contour lines play a key role in trail design. Trails that follow the contour are much more sustainable than trails that go straight up and down the slope. |
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A contour trail gently traverses a hill or sideslope. It's characterized by a gentle grade and a tread that outslopes slightly toward the low side. These features minimize tread erosion by encouraging sheet flow of water across the trail.
Subtle undulations in a trail create grade reversals and grade dips that also defend against water damage. These features diminish erosion by redirecting water off the trail.
Contour trails are sustainable, environmentally friendly and appealing to users. They thwart water damage in ways that are nearly invisible.
Straight lines are rare in nature, and they're rare in good trails. Trails should blend with the land. When building or maintaining a trail, the goal is to complement natural processes. Determine what that means for the area, then imitate it. A contour trail that snakes and dances across a hillside can be invisible from below. Trails that are pleasing to the eye are usually friendly to the land.