I was in a bad flood in West Virginia in 1985. We lost nearly all of our possessions, but it was rental property, so we were in a good position to move on.   I've bought two houses since that time. And the first thing I said the realtor each time was, "unless it's above the 500 year flood plain, I'm not interested."

In flat country, though, it might be pretty tough to find land above the 500 year plain.