There is so many way this can be interpreted in the real estate market. What I am talking about is literal. Before you buy you better know how much water you are going to be under when the “flood” comes.
The “flood” can come in 2 forms, water coming up and water coming down. The water coming up part is usually associated with event such as Tsunami or Hurricanes. When the water is pushed from large body of water, oceans or seas, on to land. The water coming down is mostly rain that exceed the drainage capacity. If you live out in the country, the soil could get saturated and water will start to build up. If you live in the city, the water has no place to go buy storm drains. And if the latter is overwhelmed, then the water is going to accumulate. The same thing if there water ended up in close large bodies of water, such as lakes or rivers, and these large bodies of water could not “dispose” of the surge fast enough. Then the water level is going to rise causing floods.
FEMA has pretty good maps to help you figure out if your property is potentially in a flood zone and how much risk you have being flooded. Although in many places these maps are not “100%” accurate. Also, when you think flood, you need to think of the “big picture”. Even if your particular spot was not flooded but everything around you is underwater, you really have no place to go and you are stuck.