I found this free resource [from FEMA] which will help real estate investors see if a potential investment property is in a flood zone or not.
Checkout http://msc.fema.gov
I recently found some interesting looking industrially-zoned commerical land in D/FW that was formally developed, and is now currently unoccupied & severely run down — while everything else around it is developed and booming. After doing a little quick research, it turned out this property is definitely in a bad flood zone and was more than likely flooded out in the past.