I recently started woring with World Machine, a 3D terrain generation program. Has some great tools. Below is a sreenshot of my first attempt at applying an erosion filter to a heightfield terrain created in VUE.
VUE (version 11) has for generating fractal terrains, both Procedural and Heightfield, but the filtering options are limited. The erosion functions in VUE don't do a great job at this point. But World Machine is another story.