The project started in World Creator, a stand alone program for terrain generation/deformation. From there I was able to generate a height map and distribution maps.
In Blender, the height map was used to drive a deform modifier on a subdivided plane; creating the terrain mesh.
The distribution maps were used as masks to mix together shaders to for the terrain material.
The distribution maps were also used as masks within geometry nodes, distributing points only in areas appropriate for vegetation, sedimentation, etc, with assets then instanced to those points.
