Definition of a Beach

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Definition of a Beach

Warin
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: The 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? Merseyside?https://www.adelaidenow.com.au/news/national/rnli-rescue-dog-walker-stuck-in-mud-on-merseyside-beach/video/f52508898923c2dc9907202049229bbe
 https://www.niwa.co.nz/coasts-and-oceans/nz-coast/learn-about-coastal-environments/beach-types/13-beach-types/reflective-tidal-mud-flats

    
What about rock? 
https://www.weekendnotes.com/marino-rocks-beach/ 


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Re: Definition of a Beach

Joseph Eisenberg
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
relevant.

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.

-Joseph

On 8/15/19, Warin <[hidden email]> 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?
> Merseyside?https://www.adelaidenow.com.au/news/national/rnli-rescue-dog-walker-stuck-in-mud-on-merseyside-beach/video/f52508898923c2dc9907202049229bbe
>
>
> https://www.niwa.co.nz/coasts-and-oceans/nz-coast/learn-about-coastal-environments/beach-types/13-beach-types/reflective-tidal-mud-flats
>
> What about rock?
>
> https://www.weekendnotes.com/marino-rocks-beach/
>
>

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Re: Definition of a Beach

Mateusz Konieczny-3



15 Aug 2019, 03:43 by [hidden email]:
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.
edit that claimed that beach is well defined by
"Unvegetated strip of land at the edge of water."

Main problem with such definition is that strip of concrete/asphalt along shore
is not a beach.

I thought about dunes when I claimed that "beach is not
always unvegetated" but now I see that dunes are not considered as part of the beach.

I copied definition from Wikipedia as it seemed far better as it managed to
exclude stuff like



Maybe copying previous definition from natural=beach would be preferable.

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
relevant.

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.
So it seems that maybe I managed to improve it, but purely by accident.

Overall I am fine also with older definition from natural=beach, page but I strongly
oppose defining beaches as "Unvegetated strip of land at the edge of water."

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Re: Definition of a Beach

Warin
On 15/08/19 14:16, Mateusz Konieczny wrote:



15 Aug 2019, 03:43 by [hidden email]:
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.
edit that claimed that beach is well defined by
"Unvegetated strip of land at the edge of water."

And that was paraphrased form the original OSM description of a beach.

Main problem with such definition is that strip of concrete/asphalt along shore
is not a beach.

I thought about dunes when I claimed that "beach is not
always unvegetated" but now I see that dunes are not considered as part of the beach.

I copied definition from Wikipedia as it seemed far better as it managed to
exclude stuff like



Maybe copying previous definition from natural=beach would be preferable.

Don't know .. hence my question here .. any 'beach' 'experts'? 

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
relevant.

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.
So it seems that maybe I managed to improve it, but purely by accident.

Overall I am fine also with older definition from natural=beach, page but I strongly
oppose defining beaches as "Unvegetated strip of land at the edge of water."

Good point about concrete may not be a 'beach' .. but then what is a 'beach'?



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Re: Definition of a Beach

Graeme Fitzpatrick

On Thu, 15 Aug 2019 at 14:50, Warin <[hidden email]> wrote:
On 15/08/19 14:16, Mateusz Konieczny wrote:
Main problem with such definition is that strip of concrete/asphalt along shore
is not a beach.

I thought about dunes when I claimed that "beach is not
always unvegetated" but now I see that dunes are not considered as part of the beach.

I copied definition from Wikipedia as it seemed far better as it managed to
exclude stuff like



Maybe copying previous definition from natural=beach would be preferable.

Don't know .. hence my question here .. any 'beach' 'experts'? 

Lived beside them all my life so I'll have a go! 

I'll agree with Mateusz that concrete & boulders aren't a beach - a couple of those examples I'd probably call man_made=groyne + natural=rock (& yes, that's because it then renders as rock!), however you can have (isolated) boulders on a beach.

What is a beach though is a bit tricky, especially for OSM.

It would usually be "the area above the Low Tide mark" but that then clashes with OSM Coastline, which is taken as the High Tide mark, so that would then have to mean that the beach is 

"The area between the High Tide mark & any adjoining vegetation / structures / landforms". It's usually largely unvegetated (but may have isolated trees, clumps of grass etc), & is made up of natural materials such as sand, pebbles, shells etc"

How's that sound?

Thanks

Graeme

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Re: Definition of a Beach

Joseph Eisenberg
Re: > “It would usually be "the area above the Low Tide mark”

Agreed. Many people map this way, which means that the part of the beach between the low tide and hight tide lines is outside of the coastline. The Openstreetmap-carto style was recently changed to handle this.

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Where should

Leif Rasmussen
In reply to this post by Graeme Fitzpatrick
Was Re: [Tagging] Definition of a Beach

> that then clashes with OSM Coastline, which is taken as the High Tide mark

I was under the impression that the definition of the coastline was the average between high and low, not the high tide mark, based on what I had read on some wiki page.  I think that there must be conflicting guidelines on the wiki since I've noticed two conflicting mapping styles.  

What style do people think is better?  Is there an advantage to one over the other?  

Also, is there a good way to map the coastline as an area representing the low tide to high tide difference?  Adding some tag like tidal=yes to areas representing that shape is the best I've found, but tidal=yes can also be used to mark that some water or marsh is tidal.

Thanks,
Leif Rasmussen



On Thu, Aug 15, 2019, 8:02 AM Graeme Fitzpatrick <[hidden email]> wrote:

On Thu, 15 Aug 2019 at 14:50, Warin <[hidden email]> wrote:
On 15/08/19 14:16, Mateusz Konieczny wrote:
Main problem with such definition is that strip of concrete/asphalt along shore
is not a beach.

I thought about dunes when I claimed that "beach is not
always unvegetated" but now I see that dunes are not considered as part of the beach.

I copied definition from Wikipedia as it seemed far better as it managed to
exclude stuff like



Maybe copying previous definition from natural=beach would be preferable.

Don't know .. hence my question here .. any 'beach' 'experts'? 

Lived beside them all my life so I'll have a go! 

I'll agree with Mateusz that concrete & boulders aren't a beach - a couple of those examples I'd probably call man_made=groyne + natural=rock (& yes, that's because it then renders as rock!), however you can have (isolated) boulders on a beach.

What is a beach though is a bit tricky, especially for OSM.

It would usually be "the area above the Low Tide mark" but that then clashes with OSM Coastline, which is taken as the High Tide mark, so that would then have to mean that the beach is 

"The area between the High Tide mark & any adjoining vegetation / structures / landforms". It's usually largely unvegetated (but may have isolated trees, clumps of grass etc), & is made up of natural materials such as sand, pebbles, shells etc"

How's that sound?

Thanks

Graeme
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Re: Definition of a Beach

Warin
In reply to this post by Joseph Eisenberg
On 15/08/19 16:40, Joseph Eisenberg wrote:
Re: > “It would usually be "the area above the Low Tide mark”

Agreed. Many people map this way, which means that the part of the beach between the low tide and hight tide lines is outside of the coastline. The Openstreetmap-carto style was recently changed to handle this.

Some places claim a beach is there .. but it is completely covered by high tide.
So to fit their usage I would think a beach is from low tide to at least high tide ...
After all if you are there at low tide I think you'd call the area above the present water line (even though it is low tide) a beach.

A beach may extend above the hight tide mark if the surface material also continues unbroken.
I think we can agree that sand from the low tide to the hight tide mark and then to, say, a board walk is all one beach?

But what about other surfaces?
Pebbles? Pebbles up to what size (at some size they become rocks)?
And so on for other surfaces.



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Re: Where should

Warin
In reply to this post by Leif Rasmussen
On 15/08/19 16:50, Leif Rasmussen wrote:
Was Re: [Tagging] Definition of a Beach

> that then clashes with OSM Coastline, which is taken as the High Tide mark

I was under the impression that the definition of the coastline was the average between high and low, not the high tide mark, based on what I had read on some wiki page.  I think that there must be conflicting guidelines on the wiki since I've noticed two conflicting mapping styles.  

What style do people think is better?  Is there an advantage to one over the other? 

For a mapper gathering data it is much easier to estimate the high tide mark - either from being there at hi tide or estimating it from wave patterns and float-sum left behind. For low tide you'd have to get your timing right.
If you want the middle then you need both hi and low - at least twice the work. So for making the map data gathers job easiest - high tide only please.

Also, is there a good way to map the coastline as an area representing the low tide to high tide difference?  Adding some tag like tidal=yes to areas representing that shape is the best I've found, but tidal=yes can also be used to mark that some water or marsh is tidal.

Sorry but I don't map low tide ... too many other things to map! Good luck if you want to do that.

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Re: Definition of a Beach

Christoph Hormann-2
In reply to this post by Warin
On Thursday 15 August 2019, Warin wrote:
> What is a beach?
>
> [...]

The question you actually wanted to ask i think is what does
natural=beach mean in OSM.  This distinction between the meaning of a
tag in OSM and the meaning of the terms used for key and value in
English language is very important to keep in mind, in particular for
native English speakers.

I had a thorough look at use of natural=beach in OSM back when i changed
rendering in OSM-Carto and came to the conclusion that use of this is
actually reasonably close to the core scientific definition of beaches,
namely a wave formed accumulation of loose material at the shore of a
waterbody.

See also

http://blog.imagico.de/reefs-and-beaches-in-the-openstreetmap-standard-style/

There are a number of notable exceptions from this

* natural=beach is also used for human made artificial beaches where
sand does not occur naturally.  This is obvious since this is often
hard to distinguish for the casual observer without in depth research.
* some use of natural=beach for rocky shores exists but it is minimal.
* sometimes use of natural=beach extents on costal dunes which are not
water formed and therefore not part of the actual beach.
* in particular in the UK there is some atypical use of the tag - based
on historic practice and use of OS data as a source apparently - of
using natural=beach for what is indicated as 'Sand' in OS maps and
wetland=tidalflat (or historically natural=mud) for what OS maps show
as 'Mud'.  This is distinctly different from elsewhere in particular
since it uses natural=beach for sand based tidal flats - like here

https://www.openstreetmap.org/way/67573161

How can you identify a beach on the ground:

* there are waves breaking, at least at some times, at the water line.
* ground has a significant slope so waves roll up the beach and water
flows back in the typical fashion leaving a fairly smooth surface.
* the ground material grain size is somewhere between fine sand and
medium sized stones - small enough to be moved by the waves when they
are strong and large enough not to be suspended in and carried away by
the water as the waves break.
* there are no tidal channels forming in the loose material since these
are indicative of a tide dominated situation and not a wave dominated
one - such cases would be suited to map with natural=wetland +
wetland=tidalflat.

Where there is considerable variation is if and how the tidal part of a
beach is mapped.  Mainly the following variants exist:

* mapping only the part of the beach above the high water line leading
to a very narrow beach.
* the tidal part of the beach being mapped as or included in a tidal
flat.
* the beach crossing the coastline and including the tidal part.
* the coastline being placed not at the high water mark but below,
usually whereever the imagery used shows the water edge and ending the
beach at this line.

This would be good to clear up and establish a well defined and
intuitively usable mapping scheme.

--
Christoph Hormann
http://www.imagico.de/

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ael
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Re: Definition of a Beach

ael
On Thu, Aug 15, 2019 at 10:26:55AM +0200, Christoph Hormann wrote:
> On Thursday 15 August 2019, Warin wrote:
> > What is a beach?
>
> * there are waves breaking, at least at some times, at the water line.
> * ground has a significant slope so waves roll up the beach and water

I was going to comment that a beach has to meet the water at the same
level. That is maybe sort of implied above? As opposed to a cliff or
even wall.

I am not sure that a beach is required to have a "significant" slope.
Obviously it must have some non-zero slope, otherwise it will be covered
by the water (to a first approximation). But on reflection, even that
may not be true for some sections of a beach. Portions that may be
exposed at low tide could even have a negative slope, and still be a
(hazardous) beach.

ael


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Re: Definition of a Beach

Paul Allen
On Thu, 15 Aug 2019 at 12:41, ael <[hidden email]> wrote:

I was going to comment that a beach has to meet the water at the same
level. That is maybe sort of implied above? As opposed to a cliff or
even wall.

With a cliff the high water and low water marks would be coincident, or very nearly
so.  Unless there is at least enough space for somebody to stand between high-
and low-water marks, it can't be a beach.

I am not sure that a beach is required to have a "significant" slope.
Obviously it must have some non-zero slope, otherwise it will be covered
by the water (to a first approximation). But on reflection, even that
may not be true for some sections of a beach. Portions that may be
exposed at low tide could even have a negative slope, and still be a
(hazardous) beach.

I wouldn't say a slope is required, just that in the real world there will be a slope.
The point I think was trying to be made is that the slope isn't vertical or so steep
that it's difficult to walk on.  But I could be wrong.

--
Paul


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Re: Definition of a Beach

Joseph Eisenberg
If there is no slope in the area between the low and high tide line,
and no wave action, you usually get a wetland=tidalflat (mud flat), or
salt marsh, or mangroves, depending on the climate, not a beach.

- Joseph

On 8/15/19, Paul Allen <[hidden email]> wrote:

> On Thu, 15 Aug 2019 at 12:41, ael <[hidden email]> wrote:
>
>>
>> I was going to comment that a beach has to meet the water at the same
>> level. That is maybe sort of implied above? As opposed to a cliff or
>> even wall.
>>
>
> With a cliff the high water and low water marks would be coincident, or
> very nearly
> so.  Unless there is at least enough space for somebody to stand between
> high-
> and low-water marks, it can't be a beach.
>
> I am not sure that a beach is required to have a "significant" slope.
>> Obviously it must have some non-zero slope, otherwise it will be covered
>> by the water (to a first approximation). But on reflection, even that
>> may not be true for some sections of a beach. Portions that may be
>> exposed at low tide could even have a negative slope, and still be a
>> (hazardous) beach.
>>
>
> I wouldn't say a slope is required, just that in the real world there will
> be a slope.
> The point I think was trying to be made is that the slope isn't vertical or
> so steep
> that it's difficult to walk on.  But I could be wrong.
>
> --
> Paul
>

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Re: Definition of a Beach

Paul Allen
On Thu, 15 Aug 2019 at 13:06, Joseph Eisenberg <[hidden email]> wrote:
If there is no slope in the area between the low and high tide line,
and no wave action, you usually get a wetland=tidalflat (mud flat), or
salt marsh, or mangroves, depending on the climate, not a beach.

Sometimes wetland even if there is a slope. Depends on all sorts of factors.  There's
a continuum between beach and wetland.  Not a very broad one, but it's there.  Mostly
it will obviously be one or the other, but there are bound to be exceptions.  A wetland
in monsoon season might be a beach outside of that season.  Unlikely but possible.

--
Paul


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Re: Definition of a Beach

Christoph Hormann-2
In reply to this post by ael
On Thursday 15 August 2019, ael wrote:
>
> I was going to comment that a beach has to meet the water at the same
> level. That is maybe sort of implied above? As opposed to a cliff or
> even wall.

The beach being composed of loose material and being formed by water
waves implies the beach and the water level intersect and the slope
being limited.

> I am not sure that a beach is required to have a "significant" slope.

The slope necessarily forms if loose material is being deposited and
shaped by waves.  As Josef said if the slope is very small the waves
will not be the dominating force shaping the coast any more and tidal
currents will be the force shaping the area.  How steep and how wide
the slope is depends on the relationship of tides, waves and grain size
of the material.

There are of course also borderline cases to and combinations with other
coastal land forms like spits, longshore bars etc.  There might also be
artificial beach nourishment measures that modify the profile.  So
beaches will not necessarily have a continuous slope everywhere.  But a
slope on which waves break and water washes up and down with each wave
is a defining element of a beach.

--
Christoph Hormann
http://www.imagico.de/

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