Just a hint for the slope-length stuff - I suppose your problem with
slope-lengths following the contour-lines has to do with the absence of
relief in your study-area. If the distance between contour-lines is
fairly large and the change in elevation only in steps of 1 foot, you'll
get a map with 'steps'. A slope map should show this, by the way. The
4.1 version of r.slope.aspect can do a z-multiplication of your original
data, but this probably won't be much use with an elevation model made
from contour lines. My suggestion is to multiply your original contour
map with a certain factor (e.g. convert them to inches or centimeters),
run r.contour and then r.slope.aspect (4.1 version) to get a decent slope
(=gradient) map. This doesn't solve your r.watershed problem, but I suppose
that parts of the original code can be used to make slope-length and steepness
maps - you already stated that you don't need the rest, and r.watershed
is in fact very slow and the results are to my experience very much
dependent on the quality of the DEM and the size of the area involved. I
hope this gives you some idea on how to proceed. Good luck!
Philip Verhagen.
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