The only software I found were CAD (Computer Aided Drafting)programs which do 3-D modeling. Didn't look at prices but all of them that I know about run into 4 digits and are not user friendly. The websites I looked at were not nearly specific unough for what you want. Couldn't you be like me and take a wild assed guess based on the slope of the land?
In my area I would search out an old farmer and ask for his opinion. Those guys have forgotten more about the land than I will ever know. WAIT!! You are in Texas, better look for an old Rancher!!
