How to Grade a Switchback

Determine the Grade

• 1

  Determine desired trail grade. Evaluate the soil composition and drainage pattern for the slope. Generally, grades over 18 percent will be prone to erosion, so aim to keep all portions of the trail under this threshold. Even short stretches of trail exceeding 20 percent will tend to erode. If individual areas require higher grade, design steps to retain trail integrity.

• 2

  Plot the trail path on the slope using a leveling scope, poles and tape measure. The percentage of grade is determined by calculating rise over run. As you plot the trail course, use small colored flags as markers every five to seven feet. Grade should be calculated along the inner edges of trails and turns.

• 3

  Look for natural platforms and integrate them into the trail to help you avoid excavation work. Remember that your trail will have small variations in grade, and ensure that no portions are excessively steep. Be sure to perform measurements throughout this process.

Constructing Switchbacks

• 4

  Excavate the trail. Excavate fully into the hillside. Use fill to level the trail, especially at turns below the landings. As you excavate, continue to measure to avoid sections that will be prone to erosion. Install steps in excessively steep areas, along with retaining structures to keep soil in place.

• 5

  Construct the landings. Angle the trail inward toward the slope near the landings. Widen the trail and flatten it at the landings to facilitate turning. Install retaining walls and drains as necessary to maintain the integrity of landings.

• 6

  Design an effective drainage system to prevent erosion. Examine slope drainage patterns, and install pipes under trails to allow water a path of descent. Install a drainage ditch against the hillside as the trail approaches each landing to channel water around landing areas.

• 7

  Reinforce your switchbacks by installing retaining structures, using wood planks and metal stakes. Retention will be required most in areas of loose soil or where the hillside is steep adjacent to the trail.