Zone Definitions

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500 Year Flood Area

The flood elevation that has a 0.2-percent chance of being equaled or exceeded in any given year; it is not the flood that will occur once every 500 years.

Area not studied

Areas that have not been studied by FEMA.

Flood Transition Area

An area that is adjacent to a Special Flood Hazard Area, and that may be subject to development regulations.

Floodway

The area along both sides of a river, tributary, or creek including the main channel that has the strictest regulations on it because it is the area that is needed to move the 1 percent flood downstream and out of the homes or businesses that it may have flooded. The state of Washington does not allow construction in the floodway.

Floodway Fringe

The portion of the floodplain lying on either side of the floodway.

Non-Special Flood Hazard Area (NSFHA)

An area in a low to moderate risk flood zone (Zones B, C, X) that is not in any immediate danger from flooding caused by overflowing rivers or hard rains. However, it's important to note that structures within a NSFHA are still at risk.

Outside flood area

An area determined to be outside of a Special Flood Hazard Area, and considered to be a moderate or low risk flood area.

Special Flood Hazard Area (SFHA)

A high-risk flood area that has special flood, mudflow, or flood-related erosion hazards. This area is shown on a Flood Hazard Boundary Map or a Flood Insurance Rate Map as 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 insurance is mandatory for properties in a SFHA.

Flood Zone Designations reflect the severity or type of flooding in an area. Your property may be located in a high risk zone or a low to moderate risk zone.

High Risk Zones

• A – High flood risk. Base flood elevations have not been determined. Flood insurance is mandatory and local floodplain development codes apply. These properties have a 1 percent annual chance of flooding and a 26 percent chance of flooding over the life of a 30-year mortgage.
• AE - High flood risk. Base flood elevations have been determined. Flood insurance is mandatory and local floodplain development codes apply. These properties have a 1 percent annual chance of flooding and a 26 percent chance of flooding over the life of a 30-year mortgage.
• AH – High flood risk. Base flood elevations have been determined. Flood insurance is mandatory and local floodplain development codes apply. These properties have a 1 percent annual chance of shallow flooding, usually in the form of a pond, with an average depth of one to three feet.
• AO - High flood risk. Flood insurance is mandatory and local floodplain development codes apply. River or stream flood hazard areas, and areas with a one percent or greater chance of shallow flooding each year, usually in the form of sheet flow, with an average depth or one to three feet. These areas have a 26 percent chance of flooding over the life of a 20-year mortgage.
• AR – Areas with temporarily increased flood risk due to the building or restoration of a flood control system (such as a levee or a dam). Flood insurance is mandatory, but rates will not exceed rates for unnumbered A zones if the structure is built or restored in compliance with Zone AR floodplain management regulations.

Low to Moderate Risk Zones

• X (shaded) – Area of moderate flood hazard. This flood risk is reduced, but not removed. Flood insurance is not required in this zone, but is available and local floodplain development codes may apply.
• X (unshaded) – These properties are outside the high-risk zones. This flood risk is reduced, but not removed. Flood insurance is not required in this zone, but is available and local floodplain development codes may apply.