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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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          <div dir="ltr" data-setdir="false">Hi Rafael<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>
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            <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
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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>
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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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