Q&A for How to Read a FEMA Flood Map

Jurisdictional boundaries are a collection of legislative, regulatory, political and general administrative boundaries sourced from Federal, State and Territory authorities.

In the context of the flood maps issued by the Federal Emergency Management Agency (FEMA) in the United States, the code "C" refers to an area with a flood risk defined as a "100-Year Flood Hazard Area". This refers to an area that has a 1% chance of experiencing a certain intensity level of flooding each year.

The colours represent different areas. The outlines trace a state, city, or country.

In a FEMA flood map, "EL5" indicates that the Base Flood Elevation (BFE) in that area is 5 feet. This means the building should be elevated to or above 5 feet relative to a specific vertical datum, typically the North American Vertical Datum of 1988 (NAVD88). It represents the expected water height during a 1% annual chance flood (100-year flood). The actual elevation may differ based on the reference point, so it doesn't necessarily mean 5 feet above sea level unless the vertical datum is specified as such.

Yes, "AE-EL8" on a FEMA flood map indicates the structure is in an AE flood zone with a Base Flood Elevation (BFE) of 8 feet. However, this 8 feet is measured relative to a vertical datum, often the North American Vertical Datum of 1988 (NAVD88), not necessarily above sea level. To determine if it’s 8 feet above sea level, you need to confirm which vertical datum is used in your area. The BFE represents the estimated water level during a 1% annual chance flood (100-year flood).

The line with little flags on a FEMA flood map is called the "Limit of Moderate Wave Action" (LiMWA). It indicates the inland limit where waves can reach over 1.5 feet, marking a transition between the Coastal High Hazard Area (V zone) and areas of lower flood risk.

The Gulf of Mexico is often used to illustrate flood-prone areas because many regions along its coastline, such as Texas, Louisiana, and Florida, are highly vulnerable to flooding from storm surges, hurricanes, and heavy rainfall. The Gulf serves as a clear example of how coastal areas, even those already near or below sea level, face significant flood risks during extreme weather events. Maps of these regions help explain the impact of sea level rise, storm surges, and flooding on coastal communities.

A wavy line indicates where the base flood elevation varies along a watercourse, while a straight line shows uniform flood elevation across a large area.

On FEMA flood maps, blue areas typically indicate Special Flood Hazard Areas (SFHAs) with a higher risk of flooding, often requiring flood insurance. White areas represent zones with minimal flood risk, where flood insurance may be optional.

The black solid line with black solid triangles on a FEMA flood map usually represents a levee or floodwall. This indicates a man-made structure designed to prevent flooding by blocking or diverting water. The triangles point towards the protected area. These structures reduce flood risk but do not eliminate it entirely.

If your property has two flood zones, with the house in Zone X and the driveway in Zone AE, it means that Zone X is a lower-risk area, outside the Special Flood Hazard Area (SFHA), and flood insurance is typically optional. Zone AE is a higher-risk area within the SFHA, where structures often require flood insurance and must meet elevation requirements.