I am carrying the same subject in my bag “needs clarification” … just not yet put into writing so far. We have similar tracks in our region here - not in the open grassland but more in forest areas. Tracks which are subject to constantly trickling water, following the track for some distance and then finding another way down to the next stream. Depending on weather conditions these tracks are soaked with water for many month and drying only in longer periods of dry conditions. Hard to walk and even worse to ride a bike.
Another issue are tracks covered by dry wood, scattered over the way sometimes in many layers and nearly impossible to ride by bike unless you are a pro. This deadwood problem has significantly increased over the past few years due to the hot and dry summers causing great damage to our forests.
My idea for these issues was not to define further surface tags but to make use of the obstacle key instead. For the given examples (in the opening post an above):
- surface=ground + obstacle=bog or swamp
- surface=grass + obstacle=tussock
- surface=ground + obstacle=deadwood
and the like. I am aware the obstacle key acutally is not that much in use but it could be helpful to describe such environmental features in addition to the surface and smoothness tag imho.