Talk:Tag:water=river

@Mashin:

"Areas intermittently covered by water" - I have seen natural=water + water=river + intermittent=yes used for that what seems fine. Why "Do not double tag or overlay with duplicate area of water=river or natural=water" would be needed/correct? There is difference between wetland and wetland occasionally flooded by a river. Mateusz Konieczny (talk) 06:30, 29 March 2021 (UTC)

Oh.. I wanted to say that when the area is already tagged as natural=wetland + wetland=*, we should not create a second area on top of that that has natural=water + water=river + intermittent=yes or those tags to it. It's just because wetland by definition is area that has plants and is regularly flooded as normal part of the area lifecycle (implying natural=water + intermittent=yes). I tried to link the picture, which was supposed help to illustrate it.

I came across this only a few times, particularly in Massachusetts around the mouth of Danvers River, which I think was probably done as a tagging for renderer (e.g. https://www.openstreetmap.org/way/82006627 https://www.openstreetmap.org/way/758428230).--Mashin (talk) 13:48, 29 March 2021 (UTC)

@Mateusz Konieczny: Also why would a large relation made of many outer ways be problematic? It's a standard feature made exactly for that purpose and there are many rivers (not mentioning landcover type areas or reservoirs) mapped like that. I see no disadvantage as only the segments overlapping with bbox are downloaded, but we still get full river without excessive area fragmentation, overlaps or need to draw duplicate lines. (e.g. https://www.openstreetmap.org/relation/407294 https://www.openstreetmap.org/relation/3015325) --Mashin (talk) 14:04, 29 March 2021 (UTC)

@Mashin: One multipolygon representing water area of say https://www.openstreetmap.org/relation/34392 would be (1) extremely fragile and breaking all the time and require expert knowledge to fix (2) unusuably large (3) cause lag in most editing software (4) bring no real benefits Mateusz Konieczny (talk) 15:14, 29 March 2021 (UTC)

I am not sure about editing software, but it's true that downstream processing might get complicated if one wants to make a map of a small bbox, but has to download large multipolygon. Anyways multipolygons are already used quite often for this, I don't know if the text would have any impact on that, but if you think so... --Mashin (talk) 19:29, 29 March 2021 (UTC)

Data consumers are not issue in this case. But try editing https://www.openstreetmap.org/relation/7379046 (Saimaa lake) to see the problems with humongous multipolygons Mateusz Konieczny (talk) 23:03, 29 March 2021 (UTC)

JOSM still works relatively OK, but I definitely wouldn't want to do it in iD. :D --Mashin (talk) 04:39, 30 March 2021 (UTC)

Or Vespucci, or JOSM on computer with 4GB RAM Mateusz Konieczny (talk) 17:55, 30 March 2021 (UTC)

Conflicts between river bank mapping and a lake/reservoir

Where a lake or reservoir exist with a river 'flowing through it' how is the river mapped?

1. Is the outline of the lake/reservoir taken as the same as the river?
2. Only map the centre of the river, leaving the lake/reservoir mapped as normal?
3. Map some subjective idea of where the river bank would be if the lake/reservoir were not there
4. Something else?

Me? I'd pick No 2 as being the simplest. Warin61 (talk) 07:23, 23 May 2023 (UTC) (forgot to put this on the above, so time distortion here)

Water area is tagged as water=reservoir and through it leads a way tagged as waterway=river. --Mashin (talk) 11:35, 22 May 2023 (UTC)