We want a island with rugged hills and a smooth beach. This means that we have to avoid an uniform roughness all over the terrain. Lower areas should be calculated with less octaves. This can be done by connecting the 'oc' control input of the multi fractal source with the radial gradient source. The manually to 3.5 adjusted octave parameter will now multiplied with the values from the control input.

An additional blue connection is modeling the control flow to make a parameter dependent of an other source. Here the roughness of the island depends on the hight of the hills.