Flood Zones 101 – understand how it works

Flood Zones 101 – understand how it works

The Federal Emergency Management Agency (FEMA) classifies US regions based on the flood risk or type of flood that can happen in those places. Flood zones, or FLOOD ZONES, are the areas mapped by the probability of these hazards.

Many homeowners (owners or renters) are mistaken in thinking that Flood Insurance is only needed in high risk areas. However, almost everyone lives in a house with some risk, what must be evaluated is the number of floods that can happen in a period.

There are low, moderate and high risk zones, and yet, insurance is triggered in all these regions.

Flood zones are used to determine flood insurance requirements and costs.

What is a Special Flood Hazard Area (SHFA)?

Special Flood Hazard Area, is a Special Flood Hazard Area, properties in these locations must have flood insurance. They are sorted by letters, like this: A, AO, A1-A30, AE, A99, AH, AR, AR/A, AR/AE, AR/AH, AR/AO, AR/A1-A30, V1-V30, VE and V

If your home is in any of these zones, you will be required to have flood insurance in order to get government-backed financing. If you want to finance at a private agency, they will most likely charge you for insurance as well.

Classification by letters and flood hazards

FEMA gives each zone a letter rating based on the type and probability of flooding.

Letter A or V zones are considered high risk areas with a 25% chance of flooding over a 30-year period. Those with B, C, or X grades are considered low to moderate risk zones, but they still account for 20 to 25 percent of National Flood Insurance Program (NFIP) claims each year.

Those in zones A and V may have risk subgroups denoted by another letter or number. And any property in Zone D is in an undetermined risk zone.

Let’s see how each zone works in more detail.

Flood Zone A: High risk flood zones

Flood Zone A

Flood Zones A have a 1% chance of flooding per year and a 25% chance of flooding at least once during a 30-year mortgage. Since there was no detailed hydraulic analysis in these areas, the base flood elevation and depths were not determined.

Flood Zone AO

The AO Flood Zones have been assigned a river, stream or pond flood risk designation, meaning there is a 1% chance of receiving 30 to 90cm (1 to 3 feets ) of depth of flood water each year and a 25% chance of facing the same type of flood at least once during a 30-year loan.

Flood Zone AH

The AH Flood Zones include areas of ponds with high concentrations of water, given the designation of 1% chance of annual flooding and 25% chance of at least one flood every 30 years with an average depth of 30 to 90 centimeters.

Flood Zone A1-A30

Flood Zones A1-A30 represent numbered zones on FEMA flood maps. These Flood Insurance Rate Map ( FIRM ) designations show a baseline inundation elevation relative to the National Geodetic Vertical Datum ( NGVD ), which is mean sea level in the US.

Flood Zone AE

Flood Zone AE is slowly replacing the zones numbered A above and represents similar designations in the FIRM based on NGVD base flood elevations.

Flood Zone A99

The A99 flood zone is unique in its distinction because it represents areas in the country with a 1% chance of annual flooding and are protected by a federal flood control system mandated by the Flood Control Act of 1936. These systems include dikes, dams and other irrigation systems that allow water control in areas at high risk of flooding.

Flood Zone AR

AR flood zones are areas that have a nearby federal flood control system that has been decertified and is in the process of restoration or reconstruction to provide basic flood protection for the area. They also maintain a 1% chance of flooding each year.

Flood Zone V: high-risk coastal zones

Flood Zone V

Like Flood Zone A, Flood Zone V has a 1% annual chance of flooding and a 25% chance of flooding over a 30-year lease. This zone does not offer BFE for homes, but is considered high risk with mandatory flood insurance requirements.

Flood Zone VE, V1-V30

Unlike the unnumbered Flood Zone V, the numbered zones have a flood map with BFE s determined within the zone. These have the same flood probability as flood zone V and have mandatory flood insurance requirements.

Flood Insurance: 6 Flood Questions to Ask Before Moving

Zones V, VE and V1-V30 are coastal regions most at risk for storm surges, in addition to other forms of flooding. They are considered at risk by the speed of coastal waves. These are mandatory insurance zones for residents with federally supported funding.

Flood Zones B, C and X: low and moderate risk zones

Flood Zone B and Flood Zone X (shaded)

Moderate risk zones. These areas are normally protected by dikes or have shallow flood areas. The depth of the floods is on average less than thirty centimeters and the drainage is less than 1 square mile (2.5km²). These zones are not Special Flood Hazard Areas.

Flood Zone C and Flood Zone X (unshaded)

Flood Zone C and X (unshaded) are low risk areas with a 0.2% chance of an annual flood. These zones generally have minimal flooding, although there may be some pond or local drainage issues.

Zone D: undetermined areas

Flood D is designed to capture all other risk areas that are not defined by other flood zones. Regions that have not yet had risk analyzes completed, therefore without mandatory insurance. The insurance value accompanies the uncertainty of missing reports.


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