[GRASS-user] Watershed delineation

[Hamish]

Daniel Victoria escribió:
> I tried searching through the mailing list for something about
> r.terraflow and the logic in the numbering scheme but could not find
> anything. Could some kind soul brieflly explain the logic behind it?

this post by Helena indicates the table is not exported from
r.terraflow:

http://thread.gmane.org/gmane.comp.gis.grass.user/16202/focus=16228
Helena:
> r.terraflow is not designed to output basins the way r.watershed
> does. there is another code that I hope will be eventually
> contributed that takes terraflow output and creates a map of
> watershed hierarchy. 

 
>  I did find a message between Dylan and Hamish last year about
> joining the basins output from r.terraflow. Basically trya mixture
> of r.drain, v.extract or r.flow..
>
http://article.gmane.org/gmane.comp.gis.grass.user/15113/match=terraflow+logical
> 
> Hamish, have you tried using r.drain to connect the smaller basins?

not that I can recall now.

Jaime Carrera wrote:
> Well, r.watershed does have a logic behind the way in the numbering
> scheme. What you can do is wait for r.watershed to end and then using
> its watersheds delimit the r.terraflow watersheds.

An idea from this thread with Markus:
http://thread.gmane.org/gmane.comp.gis.grass.devel/20170/focus=20220

But instead of the harder v.net.iso, use r.cost with a starting point
on a stream network to find connected segments. The r.watershed stream
segments map uses the same cat number at the basins they are in so with
an extraction of an individual stream network you could run r.report to
get cat numbers of basins in the greater catchement.
I don't think it would be too hard to write a script to do that for
r.watershed with a small threshold.

> I tough about using r.terraflow with the D8 option and the use the
> flow direction output with r.water.outlet. Is that possible?
> Unfortunatelly I can't test it here because r.watershed is still
> running (+2 days) and I don't want to stop the process now that it
> reached 50%...

yes, wait for it to finish.


More links:
http://thread.gmane.org/gmane.comp.gis.grass.user/19851/focus=20054
Hamish:
> maybe Helena and Laura's comments help: 
>   http://article.gmane.org/gmane.comp.gis.grass.devel/16319
>   http://article.gmane.org/gmane.comp.gis.grass.devel/1442 
> searching the mailing lists turns up some more, such as:
>   http://thread.gmane.org/gmane.comp.gis.grass.user/16202/focus=16228



also,
http://article.gmane.org/gmane.comp.gis.grass.user/15029/
http://thread.gmane.org/gmane.comp.gis.grass.user/17865/focus=18008
http://thread.gmane.org/gmane.comp.gis.grass.user/3777/focus=3787
 and you found:
http://thread.gmane.org/gmane.comp.gis.grass.user/15048


Hamish



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