[Imports] UN Mappers import of UNSOS waterways in Somalia

[Pierre Béland]

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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