flood map

Simply, a Flood Zone Determination states which flood zone applies to a property.  Or put another way, it is ‘determined’ that your property is in a specific flood zone.  The Determinator, which is the company providing the Flood Zone Determination, will use FEMA’s flood maps, the county’s parcel maps, aerial photography, and other maps to figure out which flood zone is applicable to the property.

I use the term “100-year flood zone daily for elevation certificates, LOMA’s, and explaining flood maps.  But it doesn't mean what you might think.  It means there is a 1% chance you will see a flood like the one on the FEMA flood map each and every year.  Since 1% is also "1 out of 100", the term "100-year flood" was adopted because that's easier to talk about than rattling off a bunch of statistics.

FEMA sometimes shows a 500-year flood on their maps and that is technically the 0.2% annual chance flood.  Try saying "zero point two percent annual chance flood zone" two dozen times a day and you can see why we use the short version.