I live here, just to the East near Wright Patterson AFB. For the most part, the altitude is right at 900ft with dips and hollows down and small knolls upwards.
Google Earth will give you the rail lines available and a flat trainboard set to 900Ft (275M) would do you fine.
There are only two major rivers: the Miami River and the Mad River. Given this info you could just freelance one easily.
Bill