I forward a tagging proposal originally posted in italian here.
I often come cross objects like this: small drains usually built with logs, concrete or even train tracks. Their function is to drain downhill intermittently rain water, but they are also a kind of barrier for small wheeled vehicles. They are not necessarily connected to hydrografic networks and they do not imply a ford (as intended by the rule of “you can wet your boots”).
I do not know how to map them, “drain” is probably too much. Also, mapping these individually so far seemed overkill to me, because there are so many of them in certain areas (every few meters). Maybe it could be related to ways as a summarial property, like “well_drained=yes”, or similar.
I also didn’t find them much of an obstacle, because the path around them wasn’t smooth either (no stroller pushing anyway), while for bikes they didn’t seem they could pose an obstacle.
The closest I can put my finger on right now is traffic_calming=dip but I think I’ve seen a help site question about this before.
A tag for a small gutter too small to be called a ditch might be useful. For ones parallel to the road you’d expect them tagged as a road attribute but the ones going across might be worth dedicated geometry.