Rolling dips are excavated into the trail to convey water off the trail. This is the preferred technique to get water off an existing trail. Rolling dips are sometimes referred to as rolling grade dips or grade dips.
A rolling dip has two design goals. The first is to get the water off an existing trail and the second is to build it long enough that the rider does not know it's there.
The rolling dip consists of a lead-in section, a flat bottom section where water is conveyed off the trail, and a lead-out section. The lead-in and lead-out sections are steeper than the original trail.
The flat bottom section is turned at an angle to the trail (preferably 45 degrees or less) and sloped outward to get the water off the trail and onto the forest floor. A flat-bottom section is preferable to a v-shaped bottom because it allows water to slow down, spread out, and drop sediment on the trail.
Of all the techniques, rolling dips are the easiest to maintain, and they are the preferred method of getting water off existing trails. Rolling dips require more technical skills to build than water bars but are much more effective at removing water from the trail and require less maintenance.
Maintenance and Management Considerations
Inspect the rolling dip to ensure that it has maintained its shape and structural features (lead-in and lead-out and flat-bottom sections). Remove any sediment that may have deposited in the flat-bottom section and place it on the lead-in and lead-out sections of the dip. Maintain a 2 to 5 percent minimum cross slope on the drain portion of the dip to drain the water off the trail. Of all the techniques, the rolling dip is the easiest to maintain.
- Trail Building Tips – Water Management to Minimize Erosion [PDF]
- Trail Construction and Maintenance Notebook
- Road and Trail Treatments [PDF]
- Tends to be self-cleaning.
- Provides sediment that can be recovered and used for trail maintenance.
- Provides a fun-to-ride feature of the trail.
- Tends to be the preferred method of getting water off existing trail and it is the easiest to maintain.
- Requires a longer length of trail section than other techniques to remove water from the trail.
- Requires more technical skills to build than water bars but are much more effective at removing water from the trail.
- Cross slopes - inslope and outslope.
- Ditches, lead offs, and sumps.