[Tagging] Definition of a Beach
joseph.eisenberg at gmail.com
Thu Aug 15 01:43:20 UTC 2019
For context: yesterday Mateusz Konieczny edited the description of
natural=beach on the Landuse page and commented that "beach is not
always unvegetated and concrete along shore is not a beach", and then
I used his new description on the natural=beach page.
Re: > "Is mud not a beach?"
Generally beaches are formed from sand or larger mineral particles, up
to cobble-sized stones, deposited by moving water. Smaller mineral
particles are carried away by the water.
Mud is formed from mainly wet silt and clay - these are small and very
small mineral particles (clay is so fine that it feels smooth, silt
still feels a little gritty to the touch), which only settle out in
slow moving water.
At the coastline, mud is found at tidal flats ("mud flats"), not on
beaches. These are tagged natural=wetland + wetland=tidalflat
Re: > What about rock?
In British English (and OSM), "Rock" generally means bedrock. The
images of Marino Rocks Beach show an area of round cobblestones up
higher on the sloped beach, and then areas of exposed bedrock lower
down. Solid rock can be mapped as natural=bare_rock (this rock is
probably outside of the coastline, but that's ok if it's above the low
tide line), and the beach area (loose stones) with natural=beach +
surface=stones or =shingle.
Sometimes you also find rough, jagged stones next to a beach where
they have fallen from a cliff: this can be mapped as natural=scree.
Along rivers, areas of rounded stones and pebbles are usually mapped
as natural=shingle rather than natural=beach.
Re: > "To me it does not have plants growing on it - so unvegetated."
I agree that beaches generally don't have surface plants like grass -
this can be found in wind-formed sand dunes next to some beaches,
which I would map as natural=sand or natural=dune + surface=grass if
However, there are many beaches shaded by coconut palms and other
spreading or leaning trees here in the rainy tropics - the canopy
would extend out over the high tide water line, so the leaves cover a
significant part of the beach (5 or even 10 meters), and most mappers
put the boundary of natural=wood at the end of the canopy. So I don't
know if mentioning "un-vegetated" in the description is necessary.
On 8/15/19, Warin <61sundowner at gmail.com> wrote:
> What is a beach?
> Oxford Dictionary: A pebbly or sandy shore, especially by the sea
> between high- and low-water marks.
> OSM description now: landform along a body of water which consists of
> sand, shingle or other loose material
> OSM description yesterday: Unvegetated strip of sand, shingle or other loose
> material at the
> coast or the shore of a lake
> OSM text: Thenatural <https://wiki.openstreetmap.org/wiki/Key:natural>=beach
> tag is used to mark a loose geological landform along the coast or
> along another body of water consisting of sand, gravel, shingle, pebbles,
> cobblestones or sometimes shell fragments etc.
> To me it does not have plants growing on it - so unvegitated.
> Is mud not a beach?
> What about rock?
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