On 16/2/23 04:54, Greg Troxel wrote:
Andrew Davidson<thesw...@gmail.com> writes:
On 15/2/23 02:00, Greg Troxel wrote:
For wetlands, the definitions in the US:
https://www.fws.gov/media/classification-wetlands-and-deepwater-habitats-united-states
Which is:
In general terms, wetlands are lands where saturation with water is
the dominant factor determining the nature of substrate development
and the types of plant and animal communities living in the substrate
and on its surface. The single feature that most wetlands share is a
substrate that is at least periodically saturated with or covered by
water. The water creates severe physiological problems for all plants
and animals except
those that are specially adapted for such conditions.
The same definition is used in AU:
https://wetlandinfo.des.qld.gov.au/resources/static/pdf/ecology/soils/qw-soil-indicators.pdf
More or less, a wetland is characterized by being wet for at least a
portion of the growing season in a normal year. And, just because you
don't see standing water doesn't mean the soil is not wet.
I assume you are referring to this:
Yes, and I was aware of plant test above and skipped it for simplicity.
Also because it seems that if the plant species are predominately those
adapted for wet, then surely there must often be water.
Err no. There maybe water at some depth, say same metres, but surface water is
not frequent and may not be yearly.
I am thinking of the swales between sand dunes in the Simpson desert..
apparently some of them are considered 'swamps'...
If neither plants nor soil is present, then the wetland identification
must be made strictly on the basis of hydrology. In this case, the
substrate should be “saturated with water or covered by shallow water
at some time during the growing season of each year.” Cowardin et
al. (1979) fully realized how vague this hydrologic definition was
but, given the lack of detailed hydrologic data from the diversity of
wetland types, geologic regions, and climatic regions of the U.S.,
there was no
way they could have been more specific.
This is a rule of thumb that is used if the plant and soil
characteristics are not present (or if the information is not
available). It is a rule based on wetland data from the US. The
Australian ecosystem is far more fragile and inundation less often
than annually is enough to make it the dominant factor.
So, if you want to say that wetland scientists in AU consider specific
areas that do not have soil or plants but which are flooded every few
years to be natural=wetland, that sounds fine to tag it as such.
The OSM description excludes dryness for swamps.
It
won't be swamp, because that's a wetland with trees.
Swamps do not have to have trees. Tha OSM description accepts that.
"vegetation that tolerates periodic inundation or soil saturation
Or if there are
trees and AU wetland scientists call it swamp because of the
every-few-years flood being dominant, I'm ok with natural=swamp.
? flood dominate? Most of the time the 'dry' is dominate.
I do not think we should invent a new tag "dry_swamp", as that's drawing
a distinction that seems not found in the professional literature.
But 'Arid Swamp' AND 'Ephemeral Swamp; are found in the 'professional
literature'...
If there is some idea from the literature to adapt, that's ok too, but
the hierarchy of OSM should follow the hierarchy of the literature
(swamp first, subtype is less than annual, to make something up).
In which case the OSM meaning of 'wetland' must change to incorporate dry as
well as wet.
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