[GRASS-user] r.basin input using r.stream.extract output

[Margherita Di Leo]

Hi Rich,

On Thu, Apr 26, 2012 at 5:40 PM, Rich Shepard <rshepard at appl-ecosys.com>wrote:

>  The r.basin command line needs the geographic coordinates of the basin
> outlet, and these should be derived from r.stream.extract. When I look at
> the stream output from r.stream.extract (both vector and raster) with the
> HUC-12 vector boundary I see what appear to be four different outlets of
> the
> basin (see attached chicken_creek.pdf). I refer to them as north, west,
> south, and southeast.


>  Do I take this to mean that there are four basins identified by
> r.stream.extract to be described by r.basin?  For my current projects, the
> HUC-12 subbasins are the appropriate analytical units; finer resolution
> will
> add confusion rather than clarity because this is all in a regulatory
> context. My last question, then, is how do I pick an outlet point so
> r.basin
> describes the area within the vector boundary in the attached figure as a
> single basin?
>
>  The streams seem to cross the HUC-12 basin boundary at each of these
> potential basin outlet points. How should I interpret these results?
>
>  On one project I have 12 subbasins like this one; the other project has 4
> subbasins.


What you get by r.basin is the basin defined by the entire upslope area
drained by the river system into the closing section (outlet) that you
indicate by the coordinates in input. The vector layer that I can see in
your attached file doesn't look like a basin but a  portion of a sub-basin
which doesn't include the sources (the points where actually the river
begins). If you are trying to reproduce that, r.basin is not the
appropriate tool. Technically, I think the correct term of what you are
trying to delineate is inter-basin (but english native speakers can give me
an insight), while r.basin only can delineate basins and sub-basins.

HTH,
madi

>
>
> Rich
> _______________________________________________
> grass-user mailing list
> grass-user at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/grass-user
>
>


-- 
Ing. Margherita Di Leo, Ph.D.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.osgeo.org/pipermail/grass-user/attachments/20120426/7dfa1e02/attachment.html