[GRASS-user] r.watershed

GRASS GRASS user
1

Hi,

I was wondering if someone could tell me how r.watershed works in terms of creating stream network. I was of the opinion it just mapped a river from A to B based on the least cost search algorithm where elevation is the “cost”!

However, it also calculates flow directions and flow accumulations - Are these just an added bonus?

Thanks

···

Le gach dea ghui,

Shane Carey

2

Hi Shane,

I don’t know the internals of r.watershed but your best option is to take a look at the man page [1] and the references listed at the bottom. It contains all the references for the algorithms used.

Cheers

Daniel
[1] - https://grass.osgeo.org/grass72/manuals/r.watershed

On Wed, Jan 17, 2018 at 3:30 PM Shane Carey <careyshan@gmail.com> wrote:

Hi,

I was wondering if someone could tell me how r.watershed works in terms of creating stream network. I was of the opinion it just mapped a river from A to B based on the least cost search algorithm where elevation is the “cost”!

However, it also calculates flow directions and flow accumulations - Are these just an added bonus?

Thanks

–

Le gach dea ghui,

Shane Carey

grass-user mailing list
grass-user@lists.osgeo.org
https://lists.osgeo.org/mailman/listinfo/grass-user

3

On Wed, Jan 17, 2018 at 6:30 PM, Shane Carey <careyshan@gmail.com> wrote:

Hi,

I was wondering if someone could tell me how r.watershed works in terms of creating stream network. I was of the opinion it just mapped a river from A to B based on the least cost search algorithm where elevation is the “cost”!

In r.watershed, there is no “A to B”. The least cost search starts with potential outlets (many B’s) and determines flow directions for all non-NULL cells (many A’s).

However, it also calculates flow directions and flow accumulations - Are these just an added bonus?

Added bonus is flow accumulation using the determined flow directions.

Further added bonus is stream network extraction, essentially flow accumulation >= threshold.

Markus M

Thanks

–
Le gach dea ghui,
Shane Carey

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