There seems to be a massive amount of non-existent "barrier=wall" features here, in a clear attempt to make parcel boundaries visible on the map. It even looks like some kind of import, possibly by some real estate agency?? This is really low quality data, as the parcels don't even have any useful info associated with them (e.g. cadastral or address information). Remove? (at the very least the false barrier=wall tags that needlessly clutter up the map).

This waterway=dam line, and other similar features enclosing towns nearby this location, should probably be a man_made=dyke instead (osm.wiki/Tag:man_made%3Ddyke). Dams are for holding back a body of water, not flood protection like dikes.
Alternatively, a man_made=embankment might be used, if its main function is to carry a road at a higher level than the surrounding landscape.

In dit hele gebied tussen Zaandam en Beverwijk boven het Ij zijn bijna alle waterlopen met landuse=reservoir getagd, i.p.v. een toepasselijke waterway=*