Map with trail names: www.oregon.gov/odf/recreation/guides/tsf-ohv-mapside-map.pdf Map with better resolution: www.oregon.gov/odf/recreation/guides/tsf-ohv-georeferenced-trail-map.pdf Avenza is good app for georeferenced pdf maps (www.avenzamaps.com/)
That's what happens when dirt bikers find a single track they like. Erosion takes the loose dirt away, and you have a gully, that only gets deeper with age.