OK, let me start off by saying that, by no means am I one of the experts around here '-), but using drnw04a's idea I was able to, I think, achieve what you're after. If you load a terrain and then in the editor click reset, and then paint in the shape of the river you're after, rotate this terrain 180 degrees and then boolean *this* with your base terrain you will end up with something like I have done here in this capture... Hope this helps!! ==steve