Hi Ian,
Summary: For me wood is physical tree-cover and wetland is the condition
of the ground and they are complimentary rather than exclusive.
In Sweden, I map both natural=wood and natural=wetland as separate
polygons, with a common border or overlap as appropriate. There is is
very easy from aerial imagery as the trees show distinctive colour and
texture, spot checked in more easily accessible locations from field
observation of the ground below (a very important thing to do IMHO).
Here is a random example:
https://www.openstreetmap.org/#map=15/59.5708/18.3099
In Australia, I am interested indirectly through work in refining the
Murray River as it flows north of Rutherglen (VIC). I have found that
much harder so haven't yet started any systematic tree/wetland mapping,
instead focusing on the fascinating network of ox box lakes and
channels. That's partly because of the much greater cyclicity in wetness
that you allude to making wetland harder to spot and demarcate on aerial
imagery. And partly that I don't have a local field eye, (I am a
city-slicker based in Melbourne when in Australia). I am therefore
tempted to focus on wood mapping from the arm chair and leave the
wetland mapping as a more long term issue needing a reasonable degree of
local observation/knowledge.
Hope that helps, these are just my personal thoughts and I look forward
to hearing from others.
Mike
On 2020-05-12 09:37, Little Maps wrote:
Hello everyone, I don’t know if there is any right / wrong answer to
this question, hence I’m keen to know your preferences...
I’m mapping wetlands and vegetation along the Murray River upstream of
Yarrawonga, and am now mapping in Millewa forest. Millewa (in NSW) and
Barmah forest (in Vic) support large red gum forests which flood
regularly. Some areas flood annually, others less frequently. It
depends on how much water flows down the Murray and which stream
regulators in the forests are opened or closed.
My question is: would it be better to map this as a forest (i.e.
natural=wood) or as a ‘swamp’, which OSM defines as ‘an area of
waterlogged forest, with dense vegetation’, tagged as natural=wetland,
wetland=swamp, seasonal=yes. I’ve read the OSM wiki pages on both options.
I’ve made a first stab at the area
https://www.openstreetmap.org/#map=14/-35.8026/145.1484
and have mapped all but the extremes as swamp as this indicates that
the area floods regularly, which natural:wood does not show. However
most other areas on the river I’ve come across are mapped as
natural:wood with relatively small inliers for treeless wetlands and
some treed swamps.
It’s a quick job to change from wetland:swamp to natural:wood and vice
versa and I don’t hold any strong preferences myself. If the general
consensus is that the area would be better called a wood (i.e. forest)
rather than a seasonal wetland I’ll change it immediately.
(I haven’t mapped Barmah forest in Vic, as that was already mapped as
natural:wood but much of Barmah actually floods even more frequently
than Millewa).
Thanks very much for your advice. Best wishes Ian
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