Flood Insurance

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.

Only 390 counties in the US hold about 90% of the National Flood Insurance Program (NFIP) flood insurance policies.

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To put that in perspective, there are about 3,144 county and county equivalent areas in the US.  Therefore, about 12% of the counties hold about 90% of the flood insurance policies.  And there are about 169 million people living in those counties, which is 54% of the US population.