Trail Basics

Terminology

Tread: The walking surface of a trail. The impact of many footsteps compresses the soil, creating a narrow sacrifice zone that is compacted, bare and easy to follow. Tread built along hillsides is tilted slightly outward so water will run off it rather than coursing down the route and causing erosion.

Corridor:The cleared space on either side and above the tread. Maintenance crews keep trail corridors open by cutting back brush, small trees and branches so travelers have plenty of room to pass.

Backslope: The angle cut into the hillside above the inside edge of the tread. The backslope is shaped by removing soil and rocks that could slide down onto the pathway.

Downslope:The hillside below the outside edge of the tread. Like the backslope, the downslope can be a seedbed for vegetation that will stabilize the trail. It’s kept free of loose soil that could build into a berm that traps water on the tread.

Structures: Constructions that carry a trail through irregular terrain or protect it from erosion. Footbridges and long sets of rock steps climbing mountainsides can be as spectacular as they are efficient. Rock walls holding tread in place and water bars, drain dips and other erosion prevention structures can be nearly invisible to hikers who aren’t looking for them.

Grade: The steepness of a trail. Grade plays a key role in how easily a route can be hiked and also its vulnerability to erosion. The steeper a trail, the more likely rainwater and snowmelt will build up enough speed to wash out the tread. Ideally, trails never go straight down a hillside (the “fall line”) since there is no way to divert flowing water off the tread.

Switchbacks: Winding paths that make a steep terrain easier to navigate. Trail locations on steep slopes avoid the fall line by using switchbacks to turn the route back and forth as it ascends.

What makes a sustainable trail?

• Has as little impact on the environment as possible
• Integrates naturally with the surrounding landscape
• Designed and built for minimal maintenance
• Supports the trail use and demand

But how do you do that?

• Proper Location – on the sideslope
• Sustainable Grade – typically less than 10%
• Curvilinear Alignment – follows contours with regular grade reversals
• Minimal need for structures

What makes a trail unsustainable?

• Didn’t properly address the forces at play when designed or built
• Water and Gravity working against your trail
• Not designed for the use
• Doesn’t meet user satisfaction or demand
• Erosion prevalent
• Impacts to environment or wildlife
• Lack of support for the trail

GRADE REVERSALS

Grade Reversals: A grade reversal is when a climbing trail levels out and then changes direction before rising again. They are great at forcing water to drain off the trail at the grade reversal’s lowest point, even if the trail tread becomes compacted and dished out over time.