Eric,
When using the Cost Path tool to derive the path of least resistance, its my understanding that it requires two input points, A and B. It then traces the shortest path from point A to point B.
However in Arc 9.x the shortest path tool only required one input point, A, and it then traced the shortest path from point A to the edge of the DEM, which effectively becomes point B.
Therefore the shortest path tool and cost path tool are slightly different. I have a similar problem to Claire as regards tracing a surface water run-off path into the river/sea and it would be great if you could advise of a similar tool in Arc 10.
Kind regards,
Tony