- waterway=dam is fine for this purpose, additional tags should (perhaps description) could be used to map additional details. RicoZ (talk) 14:38, 17 October 2014 (UTC)
- I really think that using this for beaver dams is a bad idea, I would use natural=beaver_dam or something else ATYL. But only if I would have good reason to expect long term survival, most beaver dams are not surviving for years, from what I know. Mateusz Konieczny (talk) 20:01, 20 October 2021 (UTC)
When a highway is leading over the dam the object shouldn't mapped with both highway and waterway=dam. Best practise seems to be the dam as an area, highway through that area. When both are ways should dam and highway sharing all nodes or run parallel?--Jojo4u (talk) 17:36, 26 June 2015 (UTC)
- The common practice is to have a single way which is indeed tagged with highway and waterway=dam. Even with dam as area people may choose to have an additional waterway=dam for the top of the dam. I consider the original proposal unfortunate in that the area of the dam should be painted with waterway=dam, it would be much cleaner to have waterway=dam for the top of the dam and man_made=dam for the area. Because the area was not rendered at all for many years many people have resorted to waterway=dam+building=something instead which seems semantically cleaner.RicoZ (talk) 10:22, 27 June 2015 (UTC)
- Osmose gives a warning with highway+waterway. I think Osmose is right since something is either a dam or a highway not both. What is your reasoning using both man_made=dam and waterway=dam? IMHO a dam with a highway on top should be mapped like bridge, so perhaps highway=*+dam=yes. Double tagging waterway=dam (way and area) is plain wrong/tagging for the renderer, also using building.--Jojo4u (talk) 13:00, 27 June 2015 (UTC)
- I got confirmation by email from one of the Osmose maintainers - it was caused by an overly generic rule saying that highway=* and waterway=* are incompatible. They are going to fix this one but as usually it may take some time until the fix propagates.
- Do you see any other QA tools or validators complaining about this? RicoZ (talk) 10:22, 30 June 2015 (UTC)
- Noticed this has also been fixed in the josm validator two years ago https://josm.openstreetmap.de/ticket/8974 . RicoZ (talk) 15:01, 2 July 2015 (UTC)
- man_made=bridge is approved and in use, not quite sure what you mean. It is not rendered in mapnik yet and not needed/suitable for all bridges so not everyone uses it. The currently active man_made=bridge is a compromise for backward compatibility reasons, the improved solution when backward compatibility will no longer be an issue would be Proposed_features/Simplify_man_made=bridge_mapping #2.1 and #2.3. RicoZ (talk) 18:11, 14 July 2015 (UTC)
In "usual" GIS when waterway=dam is vectorised as a line, that line should follow the top of the dam, not the line "touching" the neighbouring landuse=reservoir. This also makes it easy to have roads/paths going over the dam - simply by adding highway=* tag to waterway=dam. Visualisation of dams tagged like that, including dams with highways:
- We (can) do it the same way when using linear dams, there is nothing saying that in OSM the dam should share a way with the reservoir. It can be done so if it is a nearly vertical thin dam where the crown of the dam is practically identical with the reservoir. If a dam as area is used things are different. RicoZ (talk) 20:24, 16 March 2019 (UTC)
- Highest point of a dam could technically be the edge of landuse=reservoir, but in most cases it is not. Without tagging waterway=dam on a highest point it is not possible to render highways over dams correctly (unless you do some data pre-processing). And it would also be incorrect to tag highway=* on the edge of landuse=reservoir as highway=* marks central line of a road which would always be at least a little bit (1/2 of road width) away from the edge of reservoir. Tstraupis (talk) 07:53, 17 March 2019 (UTC)
- I am not sure if we disagree in any way.. would you like to propose some edits to the page? The highest point of a dam and the road can be not only right at the edge of the water but even clearly inside (over) the water area - many of the really high dams are built tilted in the water direction so that their construction opposes the water pressure. Btw I think it is more common in OSM to use natural=water instead of landuse=reservoir, landuse=reservoir has a long history of discussions about its exact meaning. RicoZ (talk) 21:36, 21 March 2019 (UTC)
- My points are: a) waterway=dam should be tagged on the highway (if there is one and unless it is clearly not at the highest point) b) waterway=dam should not be tagged on the edge of reservoir unless it is actually a straight vertical dam with the highest point being above the edge of reservoir. Therefore if a dam is vertical and has a road then it would be the same line sharing attributes for dam, highway and edge of reservoir. (landuse=reservoir still the most popular way to tag reservoirs (according to taginfo 24 millions against 192 thousand) even after iD decided to support "everything blue is natural=water" scheme which introduced no advantages just confusion because of different ways to tag exactly the same things and it is off-topic here). Tstraupis (talk) 22:33, 21 March 2019 (UTC)
- Sorry for being away so long, the unfortunate deletion edit warring discussion distracted me. Those are subtle points and I think the mapper has enough freedom to do it correctly. I assume much of your concern is related to the case where a dam is mapped as a way - however it seems that in those cases where the crown of the dam is not exactly adjacent to the water it would be worthwhile to map the dam as an area instead. One thing that I would find worthwhile for dams tagged as area would be to have a way to map the crown of the dam in addition to the area of it. In retrospect the way waterway=dam is used as either way or area isn't quite ideal.. it should have been perhaps man_made=dam for the area and something else for the crown of the dam - which would be a way in most cases but an area should not be ruled out either.
- I think we should change the wording of "How to Map" to use "narrow" and "wide" instead of "smaller" and "bigger" dams and think about a way to improve the area mapping of dams? For that it would be advisable to start a new section in the talk page. RicoZ (talk) 21:10, 27 April 2019 (UTC)
- Done that  RicoZ (talk) 18:57, 11 May 2019 (UTC)
- @Jojo4u: I restricted instructions to recommend it only for cases where dam is tagged as way, not as an area. Do you think it is solved now? Mateusz Konieczny (talk) 21:26, 9 December 2020 (UTC)
Replace "wall" by "barrier"
"A wall built across a river or stream to impound the water" seems overly specific, as some dams are Rock-fill or Earth-fill dams. So I would like to suggest using barrier instead of wall. This would also be more inline with the definition on https://en.wikipedia.org/wiki/Dam --geow (talk) 20:41, 24 July 2017 (UTC)
- Mostly agree. Maybe "A wall or other barrier built...". There other open questions, what is with lakes reservoirs that have a dam all around them? RicoZ (talk) 13:51, 26 July 2017 (UTC)
- I changed to barrier Mateusz Konieczny (talk) 21:27, 9 December 2020 (UTC)
Dam Emergency Parameters?
How do we tag different types of dams constructions?
According to Wikipedia there are different types of dams constructions like arch dams, gravity dams, earth wall dams, etc. How would we different constructions for dams? Ivanatora (talk) 16:32, 1 January 2019 (UTC)
- I suggest to use ...
- .. and so on. A similar structure is used for the bridges, where there is a bridge:structure=*.--Pechristener (talk) 20:13, 13 June 2020 (UTC)
- -- Kovposch (talk) 22:12, 13 June 2020 (UTC)
- dam:structure=* is not a good solution because a dam does not have a structure like a bridge.
- Even dam:type=* is used less, it has quality content. The dam=* is an unstructured mixture of everything. There, you find 51 values yes, which do not make sense at all. Then you find livecylce tags like abadoned or destroyed and then you find reference which may point to different parts of the dam like retaining and spillway. So that tag does not really make sense.
- Therefore, I still stick to my recommendation to use dam:type=*.--Pechristener (talk) 03:53, 14 June 2020 (UTC)
- It's a matter of bad key name. Doesn't matter what are the values like. This format has always been used for general detail. dam:structure=* is simply a possibility in relation to your inspiration. I don't understand what do you mean by "a dam does not have a structure like a bridge" - Are your examples not structures? You can have dam:function=*, dam:design=*, dam:construct=*, dam:shape=*, whatever. Any word would be more specific than the useless "type". -- Kovposch (talk) 06:39, 14 June 2020 (UTC)
- In British English a dam is a type of structure. It's common to categorize dams by structure. See https://en.wikipedia.org/wiki/Dam#By_structure --Jeisenbe (talk) 17:43, 15 June 2020 (UTC)
- -- Kovposch (talk) 22:12, 13 June 2020 (UTC)
Gates in a dam
There appear to be no tag used for the flood gates in a dam. This is very common in river dams, but also somtimes in addition to a weir in earth filled dams. --Gazer75 (talk) 19:39, 8 September 2020 (UTC)
- Check that https://wiki.openstreetmap.org/wiki/Proposed_features/sluice_gate --Yann Tombmyst Tremblay (talk) 22:54, 26 May 2021 (UTC)
Tagging for wing dams?
Wing dams are rock piles or concrete barriers constructed in rivers to divert water flow to the main channel. They are supposed to help prevent sedimentation. The dams are not necessarily visible from above. They might be sitting a foot or two below water level and only be discernible by the divergent current patterns around them. Obviously, driving a boat over one of these submerged dams would bottom you out and might cause you to sink.
In the Mississippi, you can find these dams very frequently. In some areas, there might be more than one every mile. The actual locations are easy to find by consulting the USACE navigation charts.
I am wondering what the appropriate tags would be? It seems to me that waterway=dam implies that the water is actually impounded. In the case of wing dams, this isn't true. --
I found that man_made=groyne is the appropriate tag. I have never heard the word before. I don't see it mentioned anywhere in the waterway=dam page. Someone should add a reference to it for those of us that know them as wing dams. --Karsonkevin2 (talk) 14:12, 12 June 2021 (UTC)