FEMA’s flood maps divide the country into zones marked with letters. Your zone affects whether your lender requires flood insurance. It is useful to understand, but it is not the whole story.
High-risk zones (Special Flood Hazard Areas)
These areas have at least a 1% chance of flooding in any year, the so-called “100-year flood.” If you have a mortgage from a federally backed lender and your home is in one of these zones, flood insurance is required.
- Zone A: high risk, but FEMA has not calculated a detailed flood elevation.
- Zone AE: high risk, with a calculated base flood elevation (the height floodwater is expected to reach in a 1%-chance flood).
- Zone AO and AH: high risk from shallow flooding, often sheet flow on slopes or ponding, typically 1 to 3 feet deep.
- Zone V and VE: coastal high-risk areas that also face waves at least 3 feet high. Building rules here are stricter.
Moderate- and low-risk zones
- Zone X (shaded), sometimes shown as B on older maps: moderate risk, between the 1% and 0.2% annual chance flood.
- Zone X (unshaded), sometimes shown as C: lower risk, outside the 0.2% annual chance floodplain.
- Zone D: risk not yet studied.
Flood insurance is not required in these zones, but it is available, and prices are usually lower.
What a “100-year flood” really means
The name misleads many people. A 100-year flood is not one that happens once a century. It is a flood with a 1% chance of happening in any given year. Over a 30-year mortgage, that adds up to about a 26% chance of at least one such flood. Two can happen in back-to-back years.
Why the zone is not the whole story
- Flood maps are updated slowly. Some are based on studies decades old and do not reflect new building or heavier rain.
- Maps focus on rivers and coasts. Flooding from heavy rain overwhelming streets and drains often happens outside mapped zones.
- In Harris County, Texas, many homes that flooded in Hurricane Harvey in 2017 were outside the mapped high-risk zones.
Nationally, people outside high-risk zones file a large share of flood insurance claims, according to FEMA.
How to find your zone
- Go to the FEMA Flood Map Service Center (msc.fema.gov).
- Enter your address.
- View the map panel and look for the zone letter shading your property.
Many county and city websites also have easier-to-use flood map viewers. When buying a home, you can also ask for an elevation certificate, which shows how high the building sits compared with expected flood levels.
Questions people ask
Does my zone set my flood insurance price? Not directly anymore. Since 2021, FEMA’s Risk Rating 2.0 prices each home based on its own features, such as distance to water, elevation and rebuilding cost. The zone still matters for whether insurance is required.
Can I get my home removed from a flood zone? If a survey shows your home sits above the base flood elevation, you can apply to FEMA for a Letter of Map Amendment.
Where can I see my county’s flood risk? Every county page on this site shows FEMA’s inland and coastal flooding ratings, past flood declarations and flood insurance claims. See also our flood insurance guide.