The orange flag and chalk indicate where a 'drainage nick' should be built.
Drainage nicks divert water off the trail so it doesn't build up and erode a rut down the middle.
Most of the work we did was to dig new drainage nicks
The dirt we dug out of the nick was spread down the trail to fill in the rut, and also to make a gentle hump, called a 'ramp,' that further keeps water from running down the trail. It acts like a backstop.
When finished, the nick should be deep enough so that silt washed down the trail won't fill it up for several years, but gentle so that bikes can roll through it without feeling a bump.
A future drainage nick
In a few places, we widened the whole trail and filled in the center rut.
A small nick would be built here to protect the edge of the trail from erosion when the water runs off it.
Another place where water running off the trail is creating a rut on the edge. A large rainstorm could wash enough dirt out of the rut to threaten the trail.