The top and right photos are at this canal area. We think it's some sort of run off as the canal is just up at the end of this gully. Interestingly, there are roads on each side.

Bottom left is their method of erosion control. Looks like it's breaking down so I'm not sure if they will replace it or come up with a plan B. We saw this on a few of the hills on the south side of the hike.