Thank you for your comment! I perfectly agree that we should prefer a „downhill“ channel. However, there is (as far as I am concerned) no tag that indicates water movement in a man made waterway=channel. I considered waterway=river and river=canalized but that is non-standard tagging and does not resemble all „downhill channels“ either. So the combination with waterway=flowline seems to be the tagging that makes a „downhill“ movement visible in the data. — Would you mind to continue the discussion in community.openstreetmap.org?