Hmm.. Well, over here, results aren't spectacular either.. Based my approach on that Angled Strata idea, where the terrain is "tilted" by add a gradient, then terraced, and the subtracted the gradient again.. But instead of terracing it, I eroded it.. This way I would "control" the flow of the erosion... Sounds nice doesn't it?

well, It's all theory

in practice it didn't look as nice.. Basically the river erosion takes too much land out of the ground... what we want is more like getting land out of walls.. So that gave me a socnd idea.. to use the
slope selector, in conjunction with the
select angle and apply some glaciation transformation to it (
transform device). I can't say I am happy with it!.. So instead of using the transform device, I used the
expander device set to tighten.. I lost a bit of detail, but the end result was better..
The glaciation would lower the height of a wall, past below the ground's height.. It's rendering now..