<html><head></head><body><div class="ydp8a3a51ebyahoo-style-wrap" style="font-family: verdana, helvetica, sans-serif; font-size: 13px;"><div><div dir="ltr" data-setdir="false">Hi Rafael<br></div><div><br></div><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></span></div></div>
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Le jeudi 9 avril 2020 10 h 49 min 58 s UTC−4, Rafael Avila Coya <ravilacoya@gmail.com> a écrit :
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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">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">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">https://flic.kr/p/2iNyQ6G</a><br clear="none"><br clear="none">Cheers,<br clear="none"><br clear="none">Rafael.</div></div>
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