I wanted a rocky cutting and decided to use Displacement mapping to achieve it and this is how I did it. I work in max but blender also supports displacement maps.
Firstly I select a suitable tiled texture.
I then create a plane in max and add the texture to the displace function.
Then displace the plane by applying the texture.
I then add the texture to the finished model, which can be further enhanced with a normal map, if you wish.
Finally I modify the plane to create a cutting which can be lofted in the same way you would loft a viaduct or any other repeating scenery item.
Perhaps not exactly what Longbow wanted but does add some character to cuttings/cliff faces etc.