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Flood Information

Tools for Determining Special Flood Hazard Areas in Thurston County

What is a Special Flood Hazard Area?

A Special Flood Hazard Area is any area:

  • Subject to a base of one-hundred year flood (areas of special flood hazard are shown on a flood hazard boundary map or Flood Insurance Rate Map as Zone A, AO, A1-30, AE, A99, AH, VO, V1-30, VE, V).
  • High Ground Water Flood Hazard Areas Resource Map on file with the Resource Stewardship Department
  • Highest known recorded flood elevation.

 This webpage features some, but not all, of the tools Thurston County uses to determine whether a property is located within a Special Flood Hazard Area (ie, prone to river or groundwater flooding) and what the base flood elevation should be for permitting purposes. The actual presence and history of flooding determines permit requirements in unincorporated areas of Thurston County, so a variety of these methods might be used to make a determination.

The best way to find out whether your property is in a Special Flood Hazard Area is to stop by the Permit Assistance Center talk with a member of our staff.


FEMA Flood Insurance Rate Map (FIRM)

The tool used most often for determining anticipated flood levels is FEMA's Flood Insurance Rate Map (FIRM). A flood map for an area shows the elevation (number of feet) above sea level that represents the “100 year” (or 1% chance/year) flood level, known as the base flood elevation (BFE).

View the Flood Insurance Rate Map for Thurston County

To view the Flood Insurance Rate Map for Thurston County, visit the FEMA Map Service Center at www.msc.fema.gov. (Phone: 877- 336-2627.)  For help reading the Flood Insurance Rate Map, click here for FEMA's video tutorial. You  may also stop by the Thurston County Permit Assistance Center to view FEMA maps.

"FIRMettes" are also helpful tools. A FIRMette is a full-scale section of a particular portion of the FEMA Flood Insurance Rate Map (FIRM) that you create yourself online. The FEMA Map Service Center offers a helpful video tutorial on how to use this feature.

Understanding Flood Rate Map Zones

Flood Insurance Rate Maps show different floodplains with different zone designations. Governments use these zones when writing their building codes for Special Flood Hazard Areas. Click here for definitions of the various flood zones (PDF). FEMA also refers to these zones when determining which properties are required to carry flood insurance.

Map Modernizing Project Underway

The Flood Insurance Rate Maps were mapped about 20 years ago using the data that was available at the time. The FEMA Flood Map Modernization Project is converting the paper FIRMs to digital format using current topographical information. The result of the conversion will be changes to the floodplain delineations. For more information visit the state Department of Ecology's website. The new maps are referred to as "Digital Flood Insurance Rate Maps" (DFIRM).

Requesting a Change to FEMA maps

 If you believe your property has been incorrectly identified by FEMA as a Flood Hazard Area, click here for instructions to request a change. FEMA's Floodplain Management Guidebook also contains helpful information about this topic.  To find out the status of a change request, click here.


FEMA Flood Insurance Study

A Flood Insurance Study (FIS) is a book that contains information regarding flooding in a community and is developed in conjunction with the Flood Insurance Rate Map (FIRM). The FIS, also known as a flood elevation study, frequently contains a narrative of the flood history of a community and discusses the engineering methods used to develop the FIRMs. The study also contains flood profiles for studied flooding sources and can be used to determine Base Flood Elevations for some areas. For more information about Flood Insurance Studies, visit FEMA's website or stop by the Permit Assistance Center to see a paper version.


Thurston County High Groundwater MapGeodata logo

Thurston County's GeoData website features information about high ground water hazard areas and flood zones. Please click here for instructions on how to use this site.


Photos and Flood Elevation Certificates -- ie, Flood of Record

Thurston County may consult flood elevation certificates and photos of past floods to identify whether a property is within a Special Flood Hazard Area. 


Contact Us

For questions about Special Flood Hazard Areas, contact Tim Rubert at 754-3355 ext. 6647 or e-mail  rubert@co.thurston.wa.us.

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