Noise strength (DM parameter)

The 'noise strength' slider in the design map parameters wizard determines the amount of random fractal and peak noise that will be applied to your heightmap.

This is demonstrated below, where where I've made terrain with noise strengths from 0% up to 100%:

Noise strength	Heightfield	3D render
0% (left, none)
25%
50% (centre, default)
75%
100% (right, high)