Coriolis
Part of it, too, is WILBUR, the program I use for erosion and rivers. It makes for a nice product for larger land-masses, but the little coastal rivers can give a humped look to the shores of the small islands. Your point is well-taken; I'll have to think on how I can re-work these islands.
I've played with wilber with some success . You can make selections to "mask" areas from Affects and then invert that Selection and run different settings on those areas.