[GRASS-dev] r.terraflow flow direction rules

[Hamish]

Yann Chemin wrote:

> I need to route VIC hydrological model, and the routing program read
> AGNPS style flow direction. I tried to run r.watershed on my srtm
> watershed, and after a week, I just stopped it, because I needed the
> PC for other processing. (it was doing it, but slower and slower as
> it passed 60% in 3 days, 65% in 4 days etc...)

FWIW, it could speed up again and also it could finish well before 100%.
It is slow but it gets there. (for trial and error method to find the
right threshold value, you might try at a low res first then scale?)


> Now I am getting onto r.terraflow for flow direction,
> but what i need is AGNPS output, what is the flow direction type
> in r.terraflow format please.

r.terraflow uses MDF, see the pic in the r.terraflow help page and -s
flag.

for MDF -> dominant SDF, see the scripts in
http://trac.osgeo.org/grass/browser/grass-addons/raster/r.terraflow.tools/

if you don't use Matlab they can probably be made to work in Octave
without much trouble.

see d.rast.arrow's main.c for AGNPS format hints.


beware that r.terraflow sink-watershed output maps are not catchments
like you get from r.watershed.


Hamish




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