How to Read A Flood Insurance Rate Map (FIRM)

Floodwaters can endanger both life and property. Thus, it is vital to know where flood hazards exist.

A FIRM, a Flood Insurance Rate Map, is the official map of a community on which FEMA, the Federal Emergency Management Agency, has delineated both the special flood hazard areas and the flood risk premium zones applicable to the community. Communities are mapped by the Army Corps of Engineers.

In short - FIRM maps are graphical representations of  the anticipated impact floodwaters, from a 100 year storm event, would have upon your neighborhood.

A 100 year storm event or Special Flood Hazard Areas (SFHA) is a  darkly shaded area on a FIRM identifying an area with a one percent chance of being flooded in any given year.  This probability of being flooded is called the 100- year storm event  (0.1% chance of occurring) and the floodplain impacted by that flood is the SFHA. 

A Flood Map is generally presented on several pages. Those pages are known as panels. Panels depict the varying flood hazards throughout a community. Each panel includes a title box that contains the name of the community, the panel number, zone definitions, and other information include legends.  

Elevation reference marks are also found on all flood maps. These marks identify the anticipated height of a 100 year storm event relative to sea level. These elevations are usually expressed in feet; for some communities, however, the elevations are shown in meters. Descriptions of the marks, including their elevations are provided; however, descriptions of locations appear in different places, depending on the format of the Flood Map.