What? barrier=trench does not exist? that is barrier=ditch. It is not necessarily related to waterways, that would be done by an additional tag of waterway=stream. Either way, that is still a barrier.

Either way, I was able to confirm using 2024 panoramax images that this ditch indeed does not exist in the two locations the anonymous user reported.
changeset/178622580
I could not confirm the situation for way/1204168341 so that was left in.

If for whatever reason you disagree with me, please feel free to re-open this note. Also feel free to write in french, I only write in English because it's faster for me.