Displacement problems

i’m trying to create a desert like landscape, using the micropolygon displacement and i am having a ton of trouble. i just cant get the displacement in the foreground to be more detailed. right now you can even see the triangles created from the subdivision surface modifier.
if anyone has good ideas how i can get around this problem it would be really nice

https://drive.google.com/open?id=0Bwj4upeQgykHSkhfT3IwUGlwNk0