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<div class="moz-cite-prefix">I think it best to change the wiki
beach front page.<br>
<br>
At the moment only one method is mentioned ... and that is from
the hi tide and away from the water.<br>
I think the other method - from the low tide and away from the
water should be stated too. <br>
<br>
- On 04/04/18 20:58, Dave Swarthout wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAKWFYhWX+ttojcJgvDeyAVzLbaUjvOF_Gd-MZMBO2tLwqj+XSg@mail.gmail.com">
<div dir="ltr">This is an interesting problem but it has no easy
solution. Even if the Wiki definition was clear, unless you
happen to be able to measure or otherwise determine the "mean
high tide" line and other important characteristics, what we map
as beach or tidal flat is purely an approximation, especially in
areas having a large tidal range, as in Alaska where I do the
bulk of my mapping (20-30 feet). Satellite imagery may offer a
clear vision of beach and tidal flat but we cannot determine the
height of the tide when the photo was obtained. Was it at high
tide, low tide, or somewhere in between?
<div><br>
</div>
<div>I agree that a beach is a place where wave action has
created a relatively steep slope. Other areas closer to the
sea are flatter and are often composed of finer particles,
fine sand and clay, often referred to as mud. Indeed, much of
Alaska's coastline could be characterized as mud_flat due to
the large amount of solids Alaskan rivers transport to the
ocean. In my hometown of Homer, Alaska, spring low tides can
be so extreme that the water beyond the mud_flat is too
distant to see. What you can see is mud, lots of it.</div>
<div><br>
</div>
<div>Taginfo tells us that neither mud_flat or tidal_flat (or
variations without the underscore separator) are much in use,
however, for some of my mapping I've used the combination<br>
natural=wetland</div>
<div>wetland=tidalflat (but it could just as easily be
wetland=mudflat)</div>
<div><br>
</div>
<div>I've drawn those areas the best I can based on convenient
satellite imagery knowing full well it's merely a rough
approximation. There may not be a better solution.</div>
<div><br>
</div>
<div>Cheers,</div>
<div>Dave</div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Wed, Apr 4, 2018 at 4:53 PM, Warin <span
dir="ltr"><<a href="mailto:61sundowner@gmail.com"
target="_blank" moz-do-not-send="true">61sundowner@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex"><span
class="">On 04/04/18 18:18, Christoph Hormann wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
On Wednesday 04 April 2018, Warin wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
So a 'beach' may include a 'tidal flat' ... confused.<br>
</blockquote>
I tried to explain the difference - a beach is primarily
shaped by waves<br>
while a tidal flat is shaped by tidal currents.<br>
<br>
The domination of waves can usually be seen in the form
of a smooth<br>
surface where structures (like waves in the slope)
typically form<br>
parallel to the shore. Like here:<br>
<br>
<a
href="https://commons.wikimedia.org/wiki/File:The_beach_11111.JPG"
rel="noreferrer" target="_blank"
moz-do-not-send="true">https://commons.wikimedia.org/<wbr>wiki/File:The_beach_11111.JPG</a><br>
<br>
On tidal flats OTOH the water flow often form small or
large channels<br>
like here:<br>
<br>
<a
href="https://commons.wikimedia.org/wiki/File:Waikaraka_Cycleway_from_Mangere_Bridge_IV.jpg"
rel="noreferrer" target="_blank"
moz-do-not-send="true">https://commons.wikimedia.org/<wbr>wiki/File:Waikaraka_Cycleway_f<wbr>rom_Mangere_Bridge_IV.jpg</a><br>
<br>
Beaches can only form from relatively coarse material
(sand or<br>
coarser) - fine silt cannot form beaches because it does
not settle<br>
fast enough in the fast moving water so the beach would
quickly erode<br>
away. Tidal flats can form both from fine silt and
coarse sand.<br>
<br>
At coasts with a significant tidal range (like in the
UK) there is often<br>
a beach in the upper part of the tidal range with a
steeper slope and<br>
coarse sand and a tidal flat with less slope with either
sand as well<br>
or finer material.<br>
<br>
Example:<br>
<br>
<a
href="https://mc.bbbike.org/mc/?lon=-4.390229&lat=51.716636&zoom=14&num=3&mt0=bing-satellite&mt1=mapnik&mt2=google-satellite"
rel="noreferrer" target="_blank"
moz-do-not-send="true">https://mc.bbbike.org/mc/?lon=<wbr>-4.390229&lat=51.716636&zoom=1<wbr>4&num=3&mt0=bing-satellite&mt1<wbr>=mapnik&mt2=google-satellite</a><br>
</blockquote>
<br>
</span>
That is a very nice example, thanks .... I'd call them 'mud
flats' ... :)<br>
<br>
Broome, Western Australia has tides of ~10 meters and is
know for the 'Staircase to the Moon Festival'<br>
where the moon is reflected off the beach/tidal flats
ripples to form a stair case up to the moon, very pretty ...<br>
But I'm not certain if that is a tidal flat area or not ...
the imagery does not revel it ..<br>
<br>
<a
href="https://mc.bbbike.org/mc/?lon=-4.390229&lat=51.716636&zoom=14&num=3&mt0=bing-satellite&mt1=mapnik&mt2=google-satellite"
rel="noreferrer" target="_blank" moz-do-not-send="true">https://mc.bbbike.org/mc/?lon=<wbr>-4.390229&lat=51.716636&zoom=1<wbr>4&num=3&mt0=bing-satellite&mt1<wbr>=mapnik&mt2=google-satellite</a><br>
<br>
Arrr the visitors centre says tidal flats ..<br>
<a
href="http://www.visitbroome.com.au/discover/facts-figures/staircase-to-the-moon"
rel="noreferrer" target="_blank" moz-do-not-send="true">http://www.visitbroome.com.au/<wbr>discover/facts-figures/stairca<wbr>se-to-the-moon</a><br>
There are better photos of the staircase .. <a
href="http://jksj.org/2015/06/10/broome/" rel="noreferrer"
target="_blank" moz-do-not-send="true">http://jksj.org/2015/06/10/bro<wbr>ome/</a><br>
<br>
I'd still map the sand area as the beach as seen in the
imagery,<br>
think the 'tidal flat' would have one edge as the beach edge
and the rest be further out to sea.
<div class="HOEnZb">
<div class="h5"><br>
<br>
<br>
<br>
<br>
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</div>
</blockquote>
</div>
<br>
<br clear="all">
<div><br>
</div>
-- <br>
<div class="gmail_signature" data-smartmail="gmail_signature">
<div dir="ltr">Dave Swarthout<br>
Homer, Alaska<br>
Chiang Mai, Thailand<br>
Travel Blog at <a href="http://dswarthout.blogspot.com"
target="_blank" moz-do-not-send="true">http://dswarthout.blogspot.com</a></div>
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