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.

  • The Art and Science of Identifying Flood Zones - This article on page 26 of CZM’s 2002 Coastlines pdf format of Coastlines 2002 - Hurricanes
file size 4MB magazine defines coastal flood zones, explains how to use FIRMs to identify flood zones, and discusses what additional information is needed to accurately determine flood zones in areas with coastal dunes.
  • The FEMA introductory fact sheet, Using a Flood Insurance Rate Map (FIRM).
  • An animated FEMA tutorial on FIRMs.
  • The FEMA Map Services Center, which maintains copies of all FIRMs and FIS reports, and Letters of Map Change which are official changes to the effective FIRMs.
  • FEMA's FIRMette tutorial, which provides instructions for determining the flood designation for an individual parcel by creating a "FIRMette" (a section of a FIRM for a specific address or location).
  • The National Flood Insurance Program website, which has information on FISs, FIRMs, and other floodplain management issues.
  • Richard Zingarelli, Massachusetts NFIP Coordinator, who can be contacted at or (617) 626-1406 for more information on these and other NFIP topics.

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