Check out Mike Oehler's website undergroundhousing.com for books and DVD's and plans on building your underground house. They should answer all your questions on best use of your property.
I will say that his invention of the PSP method works. To this day, his original underground house,that he lived in for over 25 years, is in excellent shape, very livable and cozy.
Also note that his first experiment with underground housing was on flat ground and guess what....although his PSP method is in place, flooding is an issue. Must read, $50 & Up Underground House Book.