Flood Insurance Program

What is the Flood Insurance Program?

The National Flood Insurance Program is operated by the Federal Emergency Management Agency (FEMA). Affected cities and counties are required to participate in the national flood insurance program in order to be eligible for federal flood disaster assistance in the event of a flood. FEMA and the Army Corps of Engineers produce a flood study that identifies the Special Flood Hazard Area which is subject to inundation in the event of a 100-year flood (an event that has a 1% chance of occurrence each year). In Boise, the major source of flooding is the Boise River and foothill gulches.

When the flood study is complete and the special flood hazard area is mapped, cities are required to adopt the study and regulate development to require that all new construction is elevated with the lowest floor at or above the projected level of flooding. In addition, all federally insured mortgages for properties in the special flood hazard area are required to obtain flood insurance. FEMA offers flood insurance for those properties and the affected property owners are required to purchase it annually.

Why are new flood maps being proposed?

FEMA and the Army Corps of Engineers periodically review the adopted flood studies and update them based on the most recent topographic and development conditions. The original flood study for Boise was prepared in the 1970’s and it has been updated several times. The most recent update was in 2003. FEMA has recently completed a new study of the Boise River and has issued new flood maps that project wider flooding than previously shown because of updated accuracy and methods of data collection.

What is the Special Flood Hazard Area?

The Special Flood Hazard Area is an area subject to inundation by the 1% annual chance flood event (100-year flood). This level of flood has a 1% chance of being equaled or exceeded in any given year. There are different flood zones within the Special Flood Hazard Area:

• Floodway – The floodway is the channel of a stream plus any adjacent floodplain areas that must be kept free of encroachment so that the 100-year flood can be carried away without substantial increases in flood heights. Development is prohibited in the floodway. A good example of the protected floodway area is the Boise River.
• Floodplain/Floodway Fringe – The area between the floodway boundary and the outer limits of the 100-year flood where water is expected to pond or sheet flow. Development is allowed subject to elevation requirements within the city’s development code

What is the X-Zone?

The area outside the 100-year floodplain that has a 0.2% chance of occurring in any given year (also known as the 500-year flood).  The X zone is shown on the flood maps, but flood insurance is not required and there are no special development regulations within the city’s development code.

Where can I find a copy of the new flood maps?

Ada County has prepared an interactive GIS map that shows the new flood boundaries.  An individual can type in their address and the map will zoom in on their property.

View Map

How much does flood insurance cost?

The cost of flood insurance is based on a number of factors including the depth of flooding and the value of the affected property. The average cost of flood insurance in Boise is approximately $1,500 per year for the 100-year zones and approximately $500 for the X-zones (not required but highly suggested)

Can I purchase insurance now?

Yes, and you are encouraged to consider doing so. The national flood insurance program includes a grandfathering rule that may apply to your property.

What is the process for adoption of the new flood maps?

FEMA issued a final letter of determination on December 19, 2019. The new flood boundaries will become effective June 19, 2020 after the city adopts them into code later in spring 2020.

What will happen at the Open Houses?

City staff will be present to provide information about the new flood study and to answer questions about the flood program.

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