On 11/2/23 22:03, Jez Nicholson wrote:
The UK has plenty of areas around the coast that are deliberately not protected by flood defences so they would soak up the power of an intermittent flood. Are these a similar thing? They aren't wetlands as they aren't wet all the time.


From https://theconversation.com/why-a-wetland-might-not-be-wet-103687


"Australian wetlands have natural wet-dry cycles, with dry spells that can last for decades. Dry phases are necessary for the life cycle of the wetland itself, as well as for many of the plants and animals that live there."

"Wetlands may stay dry for many decades, while eggs and seeds wait and rest until the next flood. Some eggs (such as shield shrimp) are small enough to be dispersed by the wind, or hitch a ride on waterbirds <https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2427.2007.01901.x> leaving the area."


That sound similar to these 'flood defenses'?



On Sat, 11 Feb 2023, 10:52 Warin, <61sundow...@gmail.com> wrote:


    On 11/2/23 21:23, Jez Nicholson wrote:
    I see what you are saying, but 'dry swamp' feels slightly odd. Is
    there something like 'intermittent wetland' that is more appropriate?


    It is 'slightly odd' ... in that it is not found in populated
    parts of the globe.

    OSM tagging is written mostly by people in populated parts of the
    globe, so it suits those populated places. That is no ones fault,
    we all operate on the knowledge we have.

    Unfortunately 'dry swamps' exist and do not fit the definitions
    used in OSM exiting tags, 'wetlands' are wet.. not 'dry', 'swamps'
    are 'wet', even 'mud' is wet..

    OSM existing tags

    wetland = "A natural area subject to inundation or with
    waterlogged ground"

    Not water logged most of the time so does not fit... The
    'inundation' is very seldom.

    swamp = "An area of waterlogged forest, with dense vegetation."

    Not water logged most of the time, not a forest, and not dense
    vegetation

    mud = "Area covered with mud: water saturated fine grained soil
    without significant plant growth"

    Again not water saturated most of the time.


    On Sat, 11 Feb 2023, 10:11 Warin, <61sundow...@gmail.com> wrote:

        The ‘dry swamp’ has no apparent way to tag it. These will not
        be found in Europe, just as you don’t find deserts there.

        They have occasional water, not seasonal, not yearly but,
        say, between 5 to 20 years they have water. As such they do
        not satisfy the OSM swamp definitions at all.

        See
        https://theconversation.com/why-a-wetland-might-not-be-wet-103687
        for more on their characteristics, at least in Australia. OSM
        has access to a imagery source in Australia that maps them,
        so OSM has a legal source for them. What is needed is a tag
        for them, say, ‘natural=dry_swamp’???

        There are ~ 4,000 of these ‘natural=mud’ mapped so far that
        are in fact ‘dry swamps’. Note that the tag natural=mud  wiki
        says “This tag should not be used for areas with intermittent
        water cover which are water covered or completely dry most of
        the time.” So this tagging is incorrect as they are dry most
        of the time…


        There are more in existence but not mapped.

        Sample https://www.openstreetmap.org/way/
        <https://www.openstreetmap.org/way/1143825454>1143851993
        <https://www.openstreetmap.org/way/1143851993>


        Any thoughts?

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