[GRASS-user] Watershed divides from DEM

[Rich Shepard]

On Thu, 31 Dec 2009, Lyle E. Browning wrote:

> In my archaeological work, I will survey across 4 identical spurs of hilly
> land, of which 1 will have a large Native American component and the
> others zilch, despite all having equally level spur tips, access to water
> and the like. What makes the 4th one advantageous is that it sits astride
> a watershed divide for two typically small (5-200cfs flow) streams. The
> deer still use these to cross into the next watershed as it is the least
> exerting means of doing so. The hunters follow the deer and archaeologists
> follow the lithic scatters from the hunters.

Lyle,

   Hunters around here don't scatter lithics, but litter. Easy to follow. :-)

> Is there a way in GRASS to have it do the grunt work of finding these
> watersheds and overlaying a line or something on them such that they can
> then be accentuated and displayed?

   Many options. Start with r.watershed. The description on the man page is,
"r.watershed generates a set of maps indicating: 1) flow accumulation,
drainage direction, the location of streams and watershed basins, and 2) the
LS and S factors of the Revised Universal Soil Loss Equation (RUSLE)."

Rich