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

[Rich Shepard]

   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.

Rich
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