How to Use a Flood Zone Map

Determining your location

Since the early 1970s, the Federal Emergency Management Agency (FEMA) has been responsible for creating and updating flood zone maps for communities across the U.S. Over time, these maps have become more detailed and easier to read, helping homeowners verify whether their property is at risk of flooding. They’re also used by government officials and insurance agents to determine flood insurance requirements and policy costs. But what, exactly, does a flood zone map communicate, and how can you check if your home is in a high-risk area?

Understanding flood zone maps

Flood insurance rate maps (FIRM), known more commonly as flood zone maps, provide an overview of geographic regions and their varying levels of flood risks. In most cases, coastal and low-lying areas have the highest chance of flooding, though extreme weather can threaten homes at every elevation. Before looking up your neighborhood, it’s important to understand some of the key terms used in flood zone maps, including:

• Floodplains: Areas of low-lying ground that are adjacent to a river or other body of water, which makes them more prone to seasonal flooding.
• Special flood hazard area: Regions that FEMA has identified as having a high risk of flooding and where flood insurance is mandatory.
• Base flood elevation: The calculated elevation that floodwaters are anticipated to rise to during a base flood event, also referred to as the “1% annual chance flood” or “100-year flood,” according to FEMA.

As suggested by their name, flood zone maps are divided into “zones” that reflect the severity or type of flooding common in a given area. Each zone has its own level of flood risk and different regulations concerning flood insurance. Here’s a quick breakdown of the key flood zones you should look out for:

Moderate- to low-risk areas

• Zone B or X (shaded): Refers to regions with moderate flood hazards and base floodplains that may pose a risk to buildings and public property.
• Zone C or X (unshaded): Areas with minimal flood risks, such as those that have ponding and/or local drainage problems.

High-risk areas

• Zone AE: Regions with a 1% annual chance of flooding and a 26% chance over the life of a 30-year mortgage.
• Zone AH: Areas with a 1% annual chance of shallow flooding, usually due to ponds or other bodies of water with an average depth of 1 to 3 feet.
• Zone AO: River or stream flood hazard areas with a 1% or greater chance of flooding each year, often due to sheet flow.
• Zone AR: Any region that has a temporarily increased flood risk due to the construction or renovation of flood control systems, such as levees or dams.
• Zone V: Coastal areas that have a 1% or higher chance of flooding, along with an increased risk of storm surge.

Many states require homeowners living in high-risk flood zones to purchase insurance through the National Flood Insurance Program (NFIP), while property owners in moderate- to low-risk regions can opt out. However, most insurance experts recommend purchasing some level of flood protection even if you live outside of a high-risk area.