Stewards of Stewart
Sustainable Trails - Keep water off the trail and users on it.
The Five Essential Elements of Sustainable Trails – IMBA – 2004
1. The Half Rule:
A trail’s grade should not exceed half the grade of the hillside or side-slope that the trail traverses.
2. The Ten Percent Average Guideline:
Generally, an overall (average) trail grade of 10 percent or less is sustainable.
3. Maximum Sustainable Grade:
Although maximum sustainable trail is usually around 15 to 20 percent, it is site-specific and dependent on a number of factors – including: the Half Rule, Soil Type, Tread Make-up, Annual Rain/Snowfall, Grade Reversals, Types of Users, Number of Users, and Difficulty Level.
4. Grade Reversals:
A grade reversal is a spot at which a climbing trail levels out and drops subtly for 10 to 50 feet before rising again – water exits the trail tread at the low point of a grade reversal.
As the trail contours across a hillside, the downhill or outer edge of the trails tread should be slightly lower than the inside edge – by about five percent. Outslope encourages water to sheet across the trail rather than traveling down the trail’s center.