[Imports] UN Mappers import of UNSOS waterways in Somalia

Rafael Avila Coya ravilacoya at gmail.com
Thu Apr 9 16:59:27 UTC 2020

Hi, Pierre:

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 

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.



O 09/04/20 ás 17:48, Pierre Béland escribiu:
> Hi Rafael
> 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
> - next 20 years
> - next 100 years.
> What about something like intermittent=decade, centennial ?
> Pierre
> Le jeudi 9 avril 2020 10 h 49 min 58 s UTC−4, Rafael Avila Coya 
> <ravilacoya at gmail.com> a écrit :
> Hi:
> I've consulted a colleague expert in hydrology, and he told me about
> these fosil rivers:
> "The term fosil rivers is not widely used "scientifically", they are
> rather called Paleo channels and it is for rivers that have dried up
> since 1000s of years and most of these paleo rivers are buried or filled
> with sediments.
> If a river gets dry for any reason (let say for some decades ) but u
> could still see the river course (which is only possible in very rare
> occasions) u could still call it a river just to maintain the landmark
> notation and geography."
> I am not an expert, and I would do what Arne suggest if I was mapping
> without discussing this with anybody, but still, like Arne, I see the
> lack of a tag for these kind of rivers.
> As for the Lagh Dara, this colleague has sent me two images of the
> rivers passing by Afmadow town.
> One shows the river as we can see it normally: https://flic.kr/p/2iNyA5a
> But the second shows how it was during the 2018 devastating floodings:
> https://flic.kr/p/2iNyA7z
> He has been on UN missions in Somalia many times, so he has too on the
> ground knowledge.
> By the way: the Lagh Dera river geometry is right now of very poor
> geometry in OSM, while the UNSOS one is very good in comparison:
> https://flic.kr/p/2iNyQ6G
> Cheers,
> Rafael.
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