FEMA Flood Zone Types Explained
Every property in the United States is assigned a FEMA flood zone designation. Here's what each one means for your flood risk and insurance requirements.
Look Up Your Address âZone AE
High RiskThe most common high-risk flood zone. AE zones have a 1% annual chance of flooding (also called the 100-year flood). Base flood elevation (BFE) data is available for these areas.
AE zones are identified on FEMA Flood Insurance Rate Maps (FIRMs) and represent areas where detailed flood hazard analysis has been conducted. These areas are also known as Special Flood Hazard Areas (SFHAs).
Zone A
High RiskHigh-risk flood zone with a 1% annual chance of flooding, but without detailed base flood elevation data. These areas haven't received a full engineering analysis.
Zone A is similar to Zone AE but lacks specific BFE data. Property owners in Zone A may need to obtain a flood elevation certificate from a licensed surveyor.
Zone AH
High RiskAreas subject to shallow flooding (1â3 feet) with ponding, typically in flat terrain. Base flood elevations are shown as depths rather than elevations.
AH zones are common in areas where flood waters spread out into shallow ponds rather than flowing in channels. Common in central and western states.
Zone AO
High RiskAreas subject to shallow sheet-flow flooding, usually 1â3 feet deep. Common near alluvial fans or along rivers where floodwaters spread across flat areas.
AO zones are often found in areas near mountains or hills where water flows as a sheet across flat land rather than in defined channels.
Zone VE / V
Very High Risk â CoastalCoastal high-risk zones subject to both flooding and wave action with wave heights of 3 feet or more. These are the highest-risk zones for structural damage.
V zones are found along coastlines, typically on beaches and barrier islands. Building codes are stricter in V zones â structures must be elevated on pilings and designed to withstand wave action.
Zone X (Shaded)
Moderate RiskModerate flood hazard areas â between the 100-year and 500-year floodplains. These areas have a 0.2% annual chance of flooding. Also called Zone B on older maps.
About 25% of all flood insurance claims come from moderate-to-low risk zones. Flooding can and does happen here, often from local drainage issues rather than major flood events.
Zone X (Unshaded)
Low RiskMinimal flood hazard. Located outside the 500-year floodplain. These areas have less than a 0.2% annual chance of flooding.
Even in low-risk zones, flooding can occur from unusual weather events, ice jams, levee failures, or local drainage problems. FEMA recommends that all property owners consider flood insurance.
Zone D
UndeterminedAreas where flood hazards exist but haven't been studied or mapped. The risk is unknown but flooding is possible.
Zone D is assigned when a community has not requested a flood study or when data isn't available. Property owners should take precautions as flood risk is unknown.
What Is the 100-Year Flood?
The term "100-year flood" is commonly misunderstood. It does not mean a flood that happens once every 100 years. It means a flood that has a 1% chance of occurring in any given year.
Over the life of a 30-year mortgage, a property in a 100-year floodplain has a 26% chance of experiencing at least one flood event â more than five times the risk of fire.
Similarly, a "500-year flood" has a 0.2% annual chance and about a 6% chance over a 30-year mortgage.
How Are Flood Zones Determined?
FEMA creates Flood Insurance Rate Maps (FIRMs) by analyzing historical flood data, topography, hydrology, and land use. Engineering studies called Flood Insurance Studies (FIS) form the basis of these maps.
Not all areas of the US have been mapped with equal detail. Some areas have detailed engineering studies with precise base flood elevations, while others are mapped using less precise methods or haven't been studied at all.
FEMA continuously updates flood maps as new data becomes available, as communities develop, and as climate patterns change. Your flood zone can change â always check the most current FIRM for your property.
Can My Flood Zone Be Changed?
Yes. If you believe your property has been incorrectly mapped, you can apply for a Letter of Map Amendment (LOMA) or Letter of Map Revision (LOMR) from FEMA.
A LOMA is typically used when a property is shown in a Special Flood Hazard Area (SFHA) but the lowest ground adjacent to the structure is at or above the base flood elevation. If approved, your flood insurance requirement may be removed.
A licensed land surveyor or civil engineer can prepare an Elevation Certificate to support your LOMA application.