You can add another layer to your landscape and only use it in the foreground. Also you could separate your landscape into near and far. Adding dirt the cavities or blending the edge with a mask would help with the train rocks I think.
thanks @Benvox2 hopefully it comes out good haha. im using substance designer for the materials and then placed them depening on a slope mask created in WM and a little bit of painting to break up the repetition. here is another shot with some sand put in as well as the dirt and some corrected normals and reflectivity on…