[GRASSLIST:4431] DEM incising using drainage

[Patrick Dunlavey]

I'm wondering if anyone has any tricks for incising DEMs using drainage.
The purpose is to develop natural-looking relief shaded maps which
emphasize drainage. Accuracy of the DEM is not the goal. My thinking is
to rasterize my drainage, and then perform some manipulation on the
drainage map to produce stream channel elevation profiles that are
reasonably "realistic" (more or less "V" shaped). A further step would
be to modulate channel depths based on steepness of slope (steeper
slopes having greater incizing, flat land having very little). Finally,
I would add the drainage incizing map to the original DEM.

I'm figuring r.mapcalc would accomplish all of this. Has anyone had
experience incising DEMs? Scripts to share? Pitfalls to avoid?
Alternative approaches to suggest?

Thanks, Pat Dunlavey