I'm getting towards what I was after, but can't take it any further than this. Unfortunately (and expectedly) TG is not like Realflow

Just an experiment, so don't pay attention to the meagre landscape. The stream isn't even warped.
Something else I want to know if there's a way to make a stepped gradient. Much like strata, but with smooth edges. For rapids. But I think it'll need a PS painted image map to begin with. I know I can make one or two with smooth steps and X to scalar, sort of, but I want a way that has multiple steps (preferably variable by PF) without needing stacking of a lot of nodes.