[GRASS-user] need help computing all flow routing for large DEM

[Ken Mankoff]

On 2018-11-22 at 09:25 +0100, Markus Metz <markus.metz.giswork at gmail.com> wrote:
> On Wed, Nov 21, 2018 at 9:40 AM Ken Mankoff <mankoff at gmail.com> wrote:
>> > On 2018-11-20 at 09:56 +0100, Markus Metz
>> > <markus.metz.giswork at gmail.com>
>> >> You don't need r.watershed or r.terraflow for this purpose., You
>> >> can run r.stream.extract with a DEM as the only input, then you
>> >> get the outlets and can feed them to r.stream.basins.
>>
>> Thank you for suggesting this workflow. It works well and quickly!
>
> Strange. r.stream.extract is usually a bit slower than r.watershed.

It may very well be slower. I did not time the two. The main improvement is that the r.stream.basins addon is orders of magnitude faster than me calling r.water.outlet in a for loop (even parallelized w/ 8 cores).

  -k.