Flood zones are areas the Federal Emergency Management Agency has mapped and labeled based on their likelihood for flooding.
The Federal Emergency Management Agency (FEMA) maps areas across the country and labels them based on their flood risk or type of flooding. That’s what flood zones are in a nutshell: shorthand for how likely flooding is in any given area. Flood zones are used to determine flood insurance requirements and costs.
Many homeowners think they only need this coverage in high-risk areas, but in truth, flood insurance is for everyone. Every area is technically a flood zone – it’s just a question of how much flooding may occur. There are low, moderate, and high-risk zones, and flood claims happen in all of them.
What are the FEMA flood zones?
FEMA gives each flood zone a letter grade based on the type and likelihood of flooding. Zones designated A or V are considered high-risk areas with a one-in-four chance of flooding during a 30-year mortgage period. These areas can also have subgrades of risk denoted by another letter or number.
Areas labeled B, C, or X are considered low to moderate-risk zones, but these locations still account for more than 20% of National Flood Insurance Program claims each year. And anyone in Zone D sits in an undetermined risk zone.
Let’s look at each zone in more detail.
High-risk inland zones
Zone A denotes inland areas that are at high risk for flooding and encompasses:
High-risk coastal zones
Flood Zone V, Flood Zone VE, and Flood Zones V1-V30 are coastal regions with more risk of storm surges in addition to other forms of flooding. They’re considered at risk from the velocity of coastal waves. Flood insurance is mandatory in these zones, which means residents need flood coverage before they can get a federally backed-mortgage.
Zones B, C, and X: Low-to-moderate-risk zones
Those in Flood Zone B, Flood Zone C, and Flood Zone X live in areas with low-to-moderate flood risk and have flood insurance rates that reflect it. The overall annual risk is 0.2% or less (in other words, a 500-year flood chance). Flood insurance is typically not required in these zones, but it’s usually still a smart proactive measure.
Zone D: The great unknown
Flood D is designed to catch all other risk areas that are not defined by other flood zones. No hazard risk analysis has been done in these regions yet, so flood insurance is generally not mandatory. Flood rates in this zone reflect the uncertainty of the flood risk.
How are FEMA flood zones determined?
FEMA determines flood zones by gathering topographical information through surveys, both on the ground and in the air. On the ground, hydraulic engineers survey underwater to better understand the shape of the landscape, while in the air, scientists use LiDar, a laser-based application, to create elevation models. This information is run through computer simulations of a 100-year flood (i.e., a flood that has a 1% annual chance of happening) to create maps of how flooding may impact different areas.
Flood maps have some limitations, but they can help people understand the flood patterns that may affect their homes. Among other things, flood maps show the base flood elevations (BFE) for the zones that have them.
Which FEMA flood zones require insurance?
FEMA describes some flood zones as Special Flood Hazard Areas (SFHA). Homeowners in a SHFA have to get flood insurance if they want a mortgage backed by the federal government. Flood Zones A, AO, A1-A30, AE, A99, AH, AR, AR/A, AR/AE, AR/AH, AR/AO, AR/A1-A30, V1-V30, VE, and V are all SHFAs.
What is FEMA’s definition of a flood?
For FEMA, a flood is a temporary inundation of two or more acres or two or more properties of normally dry land caused by:
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Overflowing inland or tidal water.
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Surface water accumulation or runoff that’s quick or unusual.
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Mudslides resulting from flooding.
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Collapse of land along a lake or similar body of water that results from water-caused erosion or undermining.
One more thing to note about floods: Home insurance policies don't covere them. If you have concerns about your coverage, be sure to contact your insurance company.
