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What is a Flood Zone? FEMA Flood Zones Explained


Definition of a FEMA Flood Zone: Flood zones are geographic areas that FEMA has defined according to varying levels of flood risk. These zones are depicted on a community's Flood Insurance Rate Map (FIRM) or Flood Hazard Boundary Map. Each zone reflects the severity or type of flooding in the area.


Flood zones are used by FEMA to determine the boundary for Special Flood Hazard Areas (SFHA), which determines where the mandatory purchase of flood insurance applies. These areas are shown on the Flood Hazard Boundary Map (FHBM) or a Flood Insurance Rate Map (FIRM). FEMA also uses flood zones for flood plain management.


CATcoverage.com has not typically relied on flood zones to calculate premium since the designations have not been a reliable factor in determining flood risk. Instead, we rely on our risk algorithm which uses geospatial data to determine the likelihood of damage during a flood.


If you are a producer for CATcoverage.com and you have more questions about a property’s flood risk, feel free to contact our customer service department.


High Risk Areas

The zones in which mandatory flood insurance applies are zone A, AO, A1-A30, AE, A99, AH, AR, AR/A, AR/AE, AR/AH, AR/AO, AR/A1-A30, V1-V30, VE or V.

​Flood Zone

FEMA'S Description

A

Areas with a 1% annual chance of flooding and a 26% chance of flooding over the life of a 30‐year mortgage. Because detailed analyses are not performed for such areas; no depths or base flood elevations are shown within these zones.

AE

The base floodplain where base flood elevations are provided. AE Zones are now used on new format FIRMs instead of A1‐A30 Zones.

A1-30

These are known as numbered A Zones (e.g., A7 or A14). This is the base floodplain where the FIRM shows a BFE (old format). These zones are slowly being replaced by Zone AE.

AH

Areas with a 1% annual chance of shallow flooding, usually in the form of a pond, with an average depth ranging from 1 to 3 feet. These areas have a 26% chance of flooding over the life of a 30‐year mortgage. Base flood elevations derived from detailed analyses are shown at selected intervals within these zones.

AO

River or stream flood hazard areas, and areas with a 1% or greater chance of shallow flooding each year, usually in the form of sheet flow, with an average depth ranging from 1 to 3 feet. These areas have a 26% chance of flooding over the life of a 30‐year mortgage. Average flood depths derived from detailed analyses are shown within these zones.

AR

Areas with a temporarily increased flood risk due to the building or restoration of a flood control system (such as a levee or a dam). Mandatory flood insurance purchase requirements will apply, but rates will not exceed the rates for unnumbered A zones if the structure is built or restored in compliance with Zone AR floodplain management regulations.

A99

Areas with a 1% annual chance of flooding that will be protected by a Federal flood control system where construction has reached specified legal requirements. No depths or base flood elevations are shown within these zones.

V

​Coastal areas with a 1% or greater chance of flooding and an additional hazard associated with storm waves. These areas have a 26% chance of flooding over the life of a 30‐year mortgage. No base flood elevations are shown within these zones.

VE, V1-30

Coastal areas with a 1% or greater chance of flooding and an additional hazard associated with storm waves. These areas have a 26% chance of flooding over the life of a 30‐year mortgage. Base flood elevations derived from detailed analyses are shown at selected intervals within these zones.

Moderate to Low Risk Areas

These zones are B and X (unshaded) and C and X (shaded).

​Flood Zone

FEMA's Description

B and X (shaded)

Area of moderate flood hazard, usually the area between the limits of the 100‐year and 500‐year floods. B Zones are also used to designate base floodplains of lesser hazards, such as areas protected by levees from 100‐year flood, or shallow flooding areas with average depths of less than one foot or drainage areas less than 1 square mile.

C and X (unshaded)

Area of minimal flood hazard, usually depicted on FIRMs as above the 500‐year flood level. Zone C may have ponding and local drainage problems that don't warrant a detailed study or designation as base floodplain. Zone X is the area determined to be outside the 500‐year flood and protected by levee from 100‐year flood.

Undetermined Risk Areas

Flood zone D is an area where no flood hazard analysis has been conducted.

​Flood Zone

FEMA's Description

D

​Areas with possible but undetermined flood hazards. No flood hazard analysis has been conducted. Flood insurance rates are commensurate with the uncertainty of the flood risk


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