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.
- Interpreting Federal Emergency Management Agency Flood Maps and Studies in the Coastal Zone, which provides information on how to interpret FIRMs and FISs to better understand the potential effects of flooding on buildings, properties, and the underlying natural resource areas.
- The FEMA introductory fact sheet, Using a Flood Insurance Rate Map (FIRM) (PDF, 298 KB).
- The FEMA Flood Map Services Center, where you can view or download all FIRMs and FIS reports, as well as Letters of Map Change, which are official changes to the effective FIRMs.
- The National Flood Insurance Program website, which has information on FISs, FIRMs, and other floodplain management issues.
- Massachusetts Department of Conservation and Recreation Flood Hazard Management Program, which coordinates the NFIP program for Massachusetts.