This week, we joined Carolina Mountain Club for a day of trail maintenance on the Cat Gap Trail in Pisgah National Forest.  We loaded up bright and early and drove 6.5 miles up gravel forest service road (a treat in itself - as those roads are typically closed to vehicle traffic).  We then donned our work gloves and hard hats and hiked about a half mile in to the site where we were working with hand tools.  This type of work is slow and physically demanding.  A full work day resulted in building water diversions on a 100' section of badly cupped trail.

We learned from the section maintainer that because Pisgah National Forest is a temperate rainforest, they're no longer using water bars for water diversion.  Instead, they now use something called a rolling grade dip.  We also learned that water traveling at 2mph is 64x more destructive to the trail than water moving at 1mph.  So one of the keys to successful trail maintenance is slowing down water on the trail and diverting it off trail where it can be absorbed into the ground.  Because of the amount of rain we receive, water bars tend to fill with dirt and debris and get clogged quickly.  Once they've filled in completely, they're no longer effecting in moving water off the trail and need to be rebuilt or replaced.  Additionally, water bars and noticeable to hikers - they have to step up and over them.  A well-built rolling grade dip should be subtle enough that hikers do not notice them when they're hiking.

A Rolling Grade Dip (see diagram from US Forest Service at right) is a water diversion that's made of a fan-shaped drain followed by a ramp.  The fan-shaped drain looks like a half circle (about 10' diameter) with the wide edge being located on the downhill side of the trail.  The fan is sloped about 15% from the uphill side to the downhill side (on our trail, that was about 3-5"), which allows water to leave the trail at the downhill edge.  It is important to clear away any duff or debris present on the downhill edge of the trail, so water can drain off the trail instead of creating a puddle.  Any good soil removed from the drain or the edge of the trail can be used to built the ramp.  The ramp is a slight slope up, just down trail from the rolling grade dip.  Any water that passes the fan will be diverted off trail by the ramp.  Because of the size of the rolling grade dip, they are much slower to get clogged and need to be cleaned/maintained less frequently than water bars.

If you'd like to get more involved in trail maintenance, check out your local trail organizations for ways to get involved!  If you're local to Western NC, you can learn more about Carolina Mountain Club on their website.