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<p>Hi, Pierre:</p>
<p>I find that idea very good indeed. The only issue is to know what
the frequence/probability is. If we know that I would definitely
go for this solution.</p>
<p>I guess that this won't be possible for the huge majority of
rivers and streams, but maybe for this one there is somewhere a
record of what years it has carried water.</p>
<p>Cheers,</p>
<p>Rafael.<br>
</p>
<div class="moz-cite-prefix">O 09/04/20 ás 17:48, Pierre Béland
escribiu:<br>
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cite="mid:1046778146.5579503.1586447329236@mail.yahoo.com">
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<div dir="ltr" data-setdir="false">Hi Rafael<br>
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<div><br>
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<div dir="ltr" data-setdir="false">I am not an hydrologist
either, but I think that for such rivers we could use the
key intermittent adding to it a value that refer to the
periodicity of water resurgence. For risk of floodings, we
generally use in Canada probability of flooding in the</div>
<div dir="ltr" data-setdir="false">- next 20 years</div>
<div dir="ltr" data-setdir="false">- next 100 years.</div>
<br>
<div dir="ltr" data-setdir="false">What about something like
intermittent=decade, centennial ?<br>
</div>
<br>
<div><br>
<span style="font-style:italic;color:rgb(0, 0,
191);font-weight:bold;"> </span></div>
<span style="font-style:italic;color:rgb(0, 0,
191);font-weight:bold;"></span>
<div class="ydp8a3a51ebsignature"><span
style="font-style:italic;color:rgb(0, 0,
191);font-weight:bold;"><font style="background-color:
inherit;" face="garamond, new york, times, serif">Pierre
</font><br>
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<div id="ydp9203f91ayahoo_quoted_7174697048"
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<div> Le jeudi 9 avril 2020 10 h 49 min 58 s UTC−4, Rafael
Avila Coya <a class="moz-txt-link-rfc2396E" href="mailto:ravilacoya@gmail.com"><ravilacoya@gmail.com></a> a écrit : </div>
<div><br>
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<div>
<div dir="ltr">Hi:<br clear="none">
<br clear="none">
I've consulted a colleague expert in hydrology, and he
told me about <br clear="none">
these fosil rivers:<br clear="none">
<br clear="none">
"The term fosil rivers is not widely used
"scientifically", they are <br clear="none">
rather called Paleo channels and it is for rivers that
have dried up <br clear="none">
since 1000s of years and most of these paleo rivers are
buried or filled <br clear="none">
with sediments.<br clear="none">
<br clear="none">
If a river gets dry for any reason (let say for some
decades ) but u <br clear="none">
could still see the river course (which is only possible
in very rare <br clear="none">
occasions) u could still call it a river just to maintain
the landmark <br clear="none">
notation and geography."<br clear="none">
<br clear="none">
I am not an expert, and I would do what Arne suggest if I
was mapping <br clear="none">
without discussing this with anybody, but still, like
Arne, I see the <br clear="none">
lack of a tag for these kind of rivers.<br clear="none">
<br clear="none">
As for the Lagh Dara, this colleague has sent me two
images of the <br clear="none">
rivers passing by Afmadow town.<br clear="none">
<br clear="none">
One shows the river as we can see it normally: <a
shape="rect" href="https://flic.kr/p/2iNyA5a"
rel="nofollow" target="_blank" moz-do-not-send="true">https://flic.kr/p/2iNyA5a</a><br
clear="none">
<br clear="none">
But the second shows how it was during the 2018
devastating floodings: <br clear="none">
<a shape="rect" href="https://flic.kr/p/2iNyA7z"
rel="nofollow" target="_blank" moz-do-not-send="true">https://flic.kr/p/2iNyA7z</a><br
clear="none">
<br clear="none">
He has been on UN missions in Somalia many times, so he
has too on the <br clear="none">
ground knowledge.<br clear="none">
<br clear="none">
By the way: the Lagh Dera river geometry is right now of
very poor <br clear="none">
geometry in OSM, while the UNSOS one is very good in
comparison: <br clear="none">
<a shape="rect" href="https://flic.kr/p/2iNyQ6G"
rel="nofollow" target="_blank" moz-do-not-send="true">https://flic.kr/p/2iNyQ6G</a><br
clear="none">
<br clear="none">
Cheers,<br clear="none">
<br clear="none">
Rafael.</div>
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