text: Wondering if someone could suggest how to classify this.
  
  By the OSM definition of a building  "a building is a man-made structure with a roof" this is not a building as it has no roof. One might argue it should go under the category power/technical buildings, but I don't see any appropriate tags there.
  
  To reiterate, this is a concrete structure on a hillside, designed to control water and debris and prevent the highway below from getting blocked or flooded.
  
  If there's a suitable category then please let me know and I can go ahead and classify this and a few other similar features in the area.