Instructions
Place a northern corner of a river where you want the top of your waterfall to begin.
Arrange four dirt paths on top of the river corner. These will not be visible when you finish, so don't worry that this looks nothing like a waterfall at this point.
Place another northern river corner over the bottom half of the first river corner.
Delete the visible dirt paths. This creates the illusion of one ripple in a waterfall. Repeat layering dirt paths and river corners in order to increase the height of your fall to the size that you desire.