Waterway barrier

I´m armchair mapping looking at a waterfall with a reservoir of water blocked by a weir or dam. Seems to be a road on both sides, so it´s possible to drive.
How do I map this correctly using JOSM?

There is no different tagging in the different editors. Please move your discussion to Questions and Answers - and add the direct link to some object near the site you are talking about. Thank you very much!