As a part of the National Flood Insurance Program (NFIP), the Federal Emergency Management Agency (FEMA) periodically conducts Flood Insurance Studies (FISs) and uses the results of these studies to produce FIS reports and Flood Insurance Rate Maps (FIRMs). FIRMs show the estimated extent of flooding during a hypothetical “100-year storm” (also called a 1% storm)—a storm that has an estimated 1% chance of being equaled or exceeded during any given year. (Note: A 100-year storm can occur more than once a century.)

Correctly interpreting FIRMs and FIS reports can be complicated. See these resources for assistance.

See also Understanding the Limitations of Flood Insurance Rate Maps and Flood Insurance Study Reports.