Do you have anti-aliasing forced in your video drivers? That can cause texture problems (though I have not seen it reported for ground texture, except in the End of Time).
If that doesn't help, maybe email supportdos@larian.com, with a description of the problem and the report.zip file generated by the
D:OS support tool (for the PC version). The report will contain your saves, in addition to system info, etc, which can be deleted if file size is an issue.
