Solved! Go to Solution.
And as an additional tip when it comes to extracting stream lines from dem's...
I always create a curvature surface and use that as a weighting into the flow accumulation step.
Because of the math of the curvature function, upwardly concave areas (like a stream) are negative,
so invert the curvature output first, (X -1) so that +ve values are associated with upwardly concave areas
and -ve values indicate the top of the hill (for example).
This idea comes from a paper by Tarboten & Ames from about 1992.
Otherwise follow the steps in the hydrology section of the help files as suggested by Jim.
Cheers,
Neil