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Rendering suggestion

Just a suggestion for rendering:

Wetland symbols.png

--Ulf Mehlig 14:28, 19 November 2008 (UTC)

See also Progress notes? below. --Ulf Mehlig 11:39, 18 February 2009 (UTC)

Tidal flats

Should all tidally varying non-vegetated areas be wetland=tidalflat, even when not "flat"? That is, the area between low tide mark and high tide mark (which is already natural=coastline by current guidelines). If so, it could be clarified on the page. Alv 07:01, 20 November 2008 (UTC)

What you tag with natural=coastline is just a line, isn't it? I think that it doesn't make sense at the moment to tag anything seawards of the natural=coastline line. If the coastline is really drawn along the mean high tide level as the Tag:natural=coastline page says, there will be just a few tidal flats (or anything tidal) left outside of estuaries/large rivers for some (probably arbitrary) reason not delimited by natural=coastline. I think that, on the long run, one might want to handle the coastline thing differently but this is most probably not a high priority issue for most people (see also the abandoned proposal Proposed features/Water cover that somehow overlaps with wetland=tidalflat; natural=wetland covers rather aspects of vegetation, while Proposed features/Water cover seems to be more interested in the physical aspects). For the moment, I personally would just handle the coastline position “flexibly” where I have special interest in intertidal areas like mangroves or tidal flats below mean high tide level, and map my wetland accordingly on the landward side of the shifted coastline. This normally requires very good (field) knowledge of local conditions and will therefore be restricted to rather small areas. --Ulf Mehlig 14:07, 20 November 2008 (UTC)
(Yes it is just one line, ambiguous with my words I were.) This came up from a diary entry where some other user was tagging tidally varying beaches. It's about the only case I've found near me as the tidal range is comparably small around here. Only now did I actively notice the word "sediment", which kind of rules out anything not soft and (theoretically) flowable. Maybe I'll try to come up with some rewording or examples.
But likely I'll split the natural=beach at the high water mark and add a tidal=yes to the intertidal zone of it if I find a wide enough place. Some areas along the coast might then be natural=scree + tidal=yes or natural=cliff + tidal=yes... I'll just have to see how the renderers cope with it at present. Alv 18:15, 20 November 2008 (UTC)
There is a valid point to tag the tidal area, as most land-based maps are interested in whats above mean high water mark, while most marine maps are interested in whats below mean low water mark. Sea boundaries are also based on what is 12nm (roughly 22.2km) from mean low water mark. I find both mean high water and mean low water to be of interest. --Skippern 10:48, 17 December 2008 (UTC)


Does Osmarender really show wetland areas correctly, as indicated by Liber? What I see is that "natural=marsh" is rendered but "natural=wetland" with "wetland=marsh" (or anything else) is not (for example, [1]). --Ulf Mehlig 14:25, 17 January 2009 (UTC)

Proposed Rendering in osmarender as Rendering-area-natural-marsh-osmarender.png from the old page moved here. --Uboot 14:00, 29 January 2009 (UTC)

I think that natural=wetland shouldn't be rendered in general with that old "marsh" bitmap. We tried to differenciate between different kinds of wetlands (also to account for the "woody" types). On top of this page is a suggestion for rendering of different wetland types, which may serve as a starting point for wetland rendering. --Ulf Mehlig 18:09, 30 January 2009 (UTC)
The old marsh bitmap is transparent, suited to a land feature on top of landstuff, and it looks really weird when rendered in the middle of a tidal estuary (for wetland=tidalflat, which IMO should be a mud/sand colour with transparency or a bitmap stipple to let the wateriness show through; tidal areas are as much land as water, after all). Andygates, 08:26 15 July 2010.

Mapnik seems to 'flood' the wetland areas over e.g. lakes, even if the wetland has layer set to -1. For example, see the Mývatn-Laxá Nature Conservation Area which is marked as wetland on layer -1, however it floods over the lake: MyvatnFloodedInMapnik.png, see [2] --Tilusnet 11:58, 28 June 2011 (BST)

Layers are not the way to solve overlaping landuse and naturals, use multipolygons is a better solution, in this case, the water as inner to the wetlands outer. --Skippern 14:33, 28 June 2011 (BST)
Thanks Skippern for the tip; I changed the relations accordingly. The problem that I am encountering now is where the inner and outer polygons overlap - i.e. a lake (role=inner) is on the borderline of the conservation area (role=outer). Is there a fix without altering the borderlines of the lake/conservation area? --Tilusnet 14:49, 12 July 2011 (BST)
I am not sure what your problem is, but you should check out Relations for further information about relations. --Skippern 01:54, 16 July 2011 (BST)
This lake is on the borderline still having a rendering problem. I had a look on Multipolygon but I am not sure that interstecting polygons are fully supported in relations. --Tilusnet 10:45, 16 July 2011 (BST)

I have a lake (or rather reservoir) part of which is covered with reedbeds. The surface is made by water throughout the whole year. Currently I am marking the whole water surface with "natural=water"+"water=reservoir" and the reed bed areas with "natural=wetland"+"wetland=reedbed" so that the renderer puts reedbed signs over the water. (See Relation 3748778 (XML, Potlatch2, iD, JOSM, history, analyze, manage, gpx)) This satisfies me completely, but is it ok to map it this way? I am asking because at the page Key:wetland it is suggested for the renderer to map the reedbed with the green area. Can it make some conflict in the future? --Strider55 (talk) 13:30, 10 June 2014 (UTC)

Impact on a pedestrian/hiker

The concept of a marsh seems to apply to quite a lot of somewhat different places, from watery river deltas to a bit soft and spongy woods. Of those some are impassable on foot and others quite easily navigable. Tagwatch revealed little uses. Some marshes are more like woods, some more like heaths, but they can't be used on the same area; natural=marsh;wood seems awkward. Does anyone have ideas or knowledge of already used classification schemes other than already mentioned salt/fresh water? Add what comes to mind and then we might think of the tags...

  • Soil
    • semicompact / easily sinking
  • Water cover
    • permanent / tidal / varying / seldom / static
    • covered area: 1 % - 100 %
  • tree cover
    • common height
    • coniferous / what ever
  • lower vegetation
    • moss / hay / bushes

Alv 09:16, 25 July 2008 (UTC)

Moved here from the old page with marsh. --Uboot 14:00, 29 January 2009 (UTC)

Progress notes?

Anybody can come with a progress note? When will wetland be rendered in Mapnik? Osmarender? Kosmos? Other? When can I take a screen dump from with wetland rendered? Using Tiles@Home layer? Cyclemaps? Captionless? --Skippern 16:57, 17 February 2009 (UTC)

I presume the wetland tag has not yet been used frequently enough to be noticed by the people responsible for rendering of the main OSM sites ... --Ulf Mehlig 22:29, 17 February 2009 (UTC)
I uploaded my rendering suggestion (see above) as single bitmaps for "seamless" repetition:

I'm submitting a trac ticket ([3]) in respect to wetland rendering now ... --Ulf Mehlig 23:16, 17 February 2009 (UTC)

Apparently, mangrove areas are rendered now at certain zoom levels, using the old "marsh" pattern: [4]. --Ulf Mehlig 17:00, 13 July 2009 (UTC)
Hey, did this ever go anywhere? I'm not very clear on the process to change the renderer, but this is a great idea and wetlands really need a distinction. --Dru1138 (talk) 17:45, 11 November 2014 (UTC)
Anybody who have the tile bases in SVG format? Where can I find different wetland renderings in SVG format? --Skippern (talk) 17:07, 13 November 2014 (UTC)

About tidal and seasonal

I see there is a tag seasonal=*, what values will it hold ? Why not having a frequency=* tag ? There could be other possible frequencies than seasonal and tidal, such as exceptional (e.g. floods), intermittent (e.g. rain), controlled (by humans, e.g. dams). --Pshunter 10:36, 20 February 2009 (UTC)

Specifying inundation frequency indeed could be an improvement ("inundation_frequency=number of days per year"?). This does, however, not completely substitute "seasonal" ("inundated during rainy season" vs. "inundated by the tides 3-5 days around full and new moon": both could sum up to the same number of days per year). I think "seasonal" could hold in the most simple case just "yes"/"no", but also something like "June to September"/"06-09" (where there should be a convention whether to specify dry or wet months; the latter seems to be more logical to me). We should collect these ideas, observe for some time how they are used, and then adapt the tag description accordingly. --Ulf Mehlig 13:40, 21 February 2009 (UTC)

Salt plains + intermittent salt lakes

Should salt plains and intermittent salt lakes be tagged as salt marsh, or do we need a separate tags for this? --Skippern 13:49, 29 April 2009 (UTC)

Salt marsh is a coastal vegetation type (but locally salt-marsh-like vegetation may exist at continental sites with salty ponds etc.). I would tag salt plains (like in Utah or north Africa, I suppose?) as something different, if focus is not on vegetation (I know these areas from photographs at most, so I'm not the person to come up with a proposal). --Ulf Mehlig
I just came to think of it as somebody have proposed this in connection with a water coverage proposal, that was trying to cover many factors covered by wetland, such as tidal flats. Many of these salt plains are intermittent lakes, and thus I would think of it as wetland. I guess there will be very little vegetation in such salt plains as that high salt concentrations will kill most kinds of plants and micro-organisms, but some highly specialized local plants might exist. Vegetation should only be a guide to how to tag it, not a rule. --Skippern 13:10, 1 May 2009 (UTC)

mangroves, PGS coastline and advanced multipolygons

Just an observation for those interested: I found that multipolygons come handy when digitising mangrove areas, as one can combine segments of the coastline and the landward mangrove limit without tracing the seaward mangrove limit on top of the coastline. This is especially helpful in areas where the old PGS coastline traces in fact the landward mangrove limit, and not the shoreline itself: to fix this,

  • trace the "real" coastline via (e.g.) landsat,
  • remove "natural=coastline" tagging from the "inland" PGS ways,
  • connect the old PGS coastline and the new coastline where the mangrove border meets the shore,
  • combine segments of new+old coastline that form closed mangrove areas in a multipolygon relation (role "outer") and
  • put the "natural=wetland"/"wetland=mangrove" tags on the relation.

Examples: [5], [6] --Ulf Mehlig 21:43, 13 July 2009 (UTC)

Start of rendering (zoomlevel)

Rendering seems to be effective at zoomlevel 13 and higher only but wetlands can be quite large (for example like Relation Okavango delta (XML, Potlatch2, iD, JOSM, history, analyze, manage, gpx)) and should in my opinion get rendered at lower zoomlevels too (maybe starting at zl 9) --katpatuka 08:46, 19 September 2010 (BST)

yes, would be great. --Ulf Mehlig 21:42, 19 September 2010 (BST)
you should probably make a ticket on trac on it, sp that the mapnik and osmarender maintainers can pick it up. --Skippern 20:24, 20 September 2010 (BST)

Manmade wetlands?

Is this tag also appropriate for wetlands that are either completely created by humans or where humans exercise considerable control over the condition of the land? Good examples are Yolo Bypass ( and Sutter Bypass where seasonal floodwaters are diverted by a system of weirs and levees.

Yes --Cartinus 20:38, 24 September 2010 (BST)

Redundant tag?

In my opinion the natural=wetland tag itself is redundant. It is obvious if an area is a wetland if it has the wetland=* tag. That way, the natural=* tag can be used to indicate any vegetation. Wetlands can have many kinds of vegetation, like trees (natural=wood), heath (moor areas), grass, moss, tundra, etc. Wetlands can also be bare, so in those cases natural=mud might be applicable.

--Fsteggink 14:31, 29 January 2011 (UTC)

There are more examples of main_key=blah + blah=sub_blah in OSM. This is done for two reasons. 1) Backward compatibility. main_key=blah often exists before people get interested in the details about blah. 2) Level of detail. The first part of natural=wetland tells you this is some kind of natural area, without you (and your tool of choice) having to know all the different kind of natural areas there exist. E.g. if you only use wetland=* it would require a wetland column in osm2pgsql's default style to be able to render it as a standard "green" area.
Most wetlands don't have a uniform vegetation cover. You can then tag a big area with natural=wetland and within that smaller areas with other natural=* tags. The wetlands that do have a uniform vegetation cover can be described by their wetland=* tags. Uniformly wooded would be wetland=swamp or wetland=mangrove, uniformly mud would be wetland=mud_flat or wetland=tidalflat (Is this one word in English?), etc. --Cartinus 22:30, 29 January 2011 (UTC)


Should a "set of pools for natural evaporation of sea-water" really be tagged with natural=wetland and wetland=saltern? When the pools are man-made, I think landuse=salt_pond is the best tag. Do such pools also occur naturally and are these called "salterns"? If not, then perhaps the wetland=saltern tag should be deprecated. --T99 09:26, 22 September 2011 (BST)

As far as I know, these types of pools exists naturally, both in adjacent of sea water, and also where rivers and other fresh water sources end up to evaporate leaving only traces of salt. In southern africa at least, these inland salt lakes are called "salt pans", while these exists also other places in the world, the surroundings of Salt Lake City in USA, just as an example. Whether these salt pans and salterns are to be tagged same or differently is something that might still be an open issue. Definitely a naturally occuring saltern should be tagged differently than the man made one. --Skippern 22:26, 24 September 2011 (BST)
The oxford dictionary says: "A set of pools in which seawater is left to evaporate to make salt." According to wikipedia a saltern is also man-made. I propose to deprecate this value in the context of wetland. It was not included in the approved proposal. --Rudolf (talk) 15:29, 23 April 2014 (UTC)

Order of values

The actual list of wetland values seems not to be ordered. I will show a classification of wetland types, relating to US EPA.

  • Marshes
    • Tidal
    • Nontidal
      • Wet Meadows
      • Prairie Potholes
      • Vernal Pools
      • Playa Lakes
  • Swamps
    • Forested Swamps
      • Bottomland Hardwoods
    • Shrub Swamps
      • Mangrove Swamps
  • Bogs
    • Northern bogs
    • Pocosins
  • Fen

Do we need values for the third category, like wet_meadows/mangrove/saltmarsh/reedbed/saltern? IMHO the four main types and some subtypes of the second category, like tidal/nontidal, forested/shrubs are sufficient. Fen is missing.

--Rudolf (talk) 13:48, 14 April 2014 (UTC)

Moved values of "wetland=" to wetland=*

According to the usage in the wiki I moved the list with values of "wetland=" to wetland=*. I propose to move the discussions about values to Talk:Key:wetland.

Not applicable on relations ?

Why is this tag not applicable on relations ? Is this an error ?

In this context the multipolygon relation is considered an area as an exception. This tag is therefore applicable on multipolygon relation but not on any other relations.
Chrabros (talk) 06:04, 24 June 2016 (UTC)