From OpenStreetMap Wiki
Jump to navigation Jump to search

old content

This proposal replaces an earlier proposal --Swampwallaby 01:46, 14 December 2007 (UTC)


  • Please start discussion for current proposal here.--Swampwallaby 02:17, 14 December 2007 (UTC)
  • Looks good, a yes from me. Thanks for the time spent on the drawings! I've been using man_made=dam but this is equally logical. It would be nice, but not vital, to introduce a convention for which side is "up" and "down" for linear drawing, e.g. down is to the right of the line in the direction of drawing. This convention could then be applied to weirs and cliffs - it is cliffs that I'm really wanting if for. MikeCollinson 08:32, 14 December 2007 (UTC)
  • And another thought, this could also be used for levees perhaps or should they have there own tag? A levee is one of those long embankments along rivers in low lying areas to stop them flooding. MikeCollinson 08:32, 14 December 2007 (UTC)
    • As a none native speaker, I'm a bit confused about the differences to embankment=yes. Could someone clarify this for me? -- Ulfl 09:14, 14 December 2007 (UTC)
  • embankment=yes is a tag added that can theoretically be added to a road to indicate it is raised above the surrounding country. A levee is a stand-alone embankment with no road on top. Mike, I have seen levees drawn on maps as thick black lines, I think that would work well. For the up/down, since we have water on the right for coastlines, it would make sense to have down is to the right. --Swampwallaby 11:04, 14 December 2007 (UTC)
Excellent!! MikeCollinson 15:45, 28 December 2007 (UTC)
  • wouldn't it be cool, to map very big dams as an area? --Cbm 00:13, 29 December 2007 (UTC)


  • Voting commenced 28th December 2007
  • I Approve this proposal. --Swampwallaby 11:23, 28 December 2007 (UTC)
  • I Approve this proposal. --TomChance 11:59, 28 December 2007 (UTC)
  • I approve this proposal. --Eimai 12:26, 28 December 2007 (UTC)
  • I Approve this proposal. -- Franc 13:23, 28 December 2007 (UTC)
  • I Approve this proposal. -- MichaelK 13:25, 28 December 2007 (UTC)
  • I Approve this proposal. --Onion 14:01, 28 December 2007 (UTC)
  • I approve this proposal. Robx 15:13, 28 December 2007 (UTC)
  • I Approve this proposal. -- MikeCollinson 15:46, 28 December 2007 (UTC)
  • I Approve this proposal. -- Myfanwy 03:03, 29 December 2007 (UTC)
  • I Approve this proposal. --Cohort 03:50, 29 December 2007 (UTC)
  • I approve this proposal--Walley 22:08, 29 December 2007 (UTC)
  • I Approve this proposal. -- Ulfl 12:31, 31 December 2007 (UTC)
  • I approve this proposal. --Gummibaerli 23:37, 3 January 2008 (UTC)
  • I approve this proposal. --Cartinus 12:19, 9 January 2008 (UTC)
  • Voting close 11th January 2008
  • Proposal Approved

node for waterway=dam

--acrosscanadatrails 13:47, 17 July 2009 (UTC) in the GeoBaseNHN import, a single node can be presented for those dams which are really small, and the rivers are represented by ways rather than areas. Can I import these, even though they dont yet get rendered?

Beaver Dams?

How would i tag beaver dams? i think they're worth tagging as they last for years and often define a landscape --Dru1138 (talk) 20:43, 18 September 2014 (UTC)

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)

Constructed dam (infrastructure) should be man_made=dam

Because of ambiguity of the meaning of the word dam, the constructed barrier should rather be in the man_made=* namespace. --Skippern (talk) 16:49, 15 April 2015 (UTC)

Sounds reasonable but with 100k objects mapped this ship has sailed unless a mass-edit is made which is not worth the hassle imho. Also weir and lock_gate have the same problem.--Jojo4u (talk) 17:33, 26 June 2015 (UTC)
Historic note for reference: They could co-exist, as in the beaver dam example above (and landslide dams, etc) for natural=* features. In theory, it is only that man_made=* is assumed for waterway=dam, like many other features/tags. waterway=* in itself means a waterway feature only. The key says nothing about the value's origin. -- Kovposch (talk) 20:53, 29 February 2020 (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)
Ok, I will complain at osmose. dam+highway is correct because it is a single structure, consider it analogous to highway+bridge. Do not try to tag for Keepright or Osmose either. Tagging the walls of a dam with buidling=wall is not tagging for the renderer. RicoZ (talk) 16:46, 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 . RicoZ (talk) 15:01, 2 July 2015 (UTC)
Nobody tags man_made=bridge+highway=*. There is good reason why it's tagged highway=*+bridge=yes.--Jojo4u (talk) 22:47, 12 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:

Note: only two upper (of total five) dams do not have highway over it. Tstraupis (talk) 10:57, 16 March 2019 (UTC)

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 [1] RicoZ (talk) 18:57, 11 May 2019 (UTC)


If the dam is drawn as area with waterway=dam should it share nodes with the highway where the highway crosses it? RicoZ (talk) 15:43, 31 May 2016 (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 --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)

Dam Emergency Parameters?

We should also have satety parameters attached to the dam. Example Full Reservoir Level, Depth of Water, Capacity, Fill Level, Contact Number. thevikas (talk) 04:34, 29 September 2017 (UTC)

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)
Why don't you use something like dam:structure=* then? Even dam=* (110 instances) is better than dam:type=* (11 instances). Most of the dam=* values drop the "dam" suffix as well.
dam=* dam:type=*
-- 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 --Jeisenbe (talk) 17:43, 15 June 2020 (UTC)