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Thurston County, WA Environmental Rules: Flood Zones (2026)

Significant Restrictions

Compiled from the official code textEditor Martyn O'NeillLast verified September 2026

FEMA flood zone rules in Thurston County, WA, also called floodplain regulations or special flood hazard area (SFHA) rules, determine flood insurance requirements and elevation standards for new construction.

Key Facts

Governing section: TCC 21.54.020, Floodplain Areas
Review authority: Title 24 Critical Areas Ordinance
Ag land floodplains: Chapter 17.15 TCC applies instead
Flood maps used: Thurston County Flood Insurance Rate Maps
Adopted: Ord. 11274, 1996

FEMA Flood Zone Lookup

FEMA assigns every parcel in the U.S. a flood-hazard designation on its Flood Insurance Rate Maps (FIRMs). Zones starting with A or V are high-risk Special Flood Hazard Areas where federally backed mortgages require NFIP flood insurance. Zone X indicates moderate-to-minimal risk, where insurance is optional but often recommended. Your specific zone determines insurance cost, build elevation, and permit requirements in Thurston County, WA.

Zone	What it means	NFIP required?
A	High-risk flood area; 1% annual chance flood, no detailed analysis.	Yes
AE	High-risk; same as A but with established Base Flood Elevations.	Yes
AH	High-risk shallow flooding (1-3 ft), usually ponding.	Yes
AO	High-risk shallow flooding (1-3 ft) with sheet flow on sloping terrain.	Yes
V	High-risk coastal zone subject to wave action (no BFE).	Yes
VE	High-risk coastal zone with wave action and established BFEs.	Yes
X (shaded)	Moderate risk; between the 1% and 0.2% annual chance flood.	Recommended
X	Minimal risk; outside the 0.2% annual chance floodplain.	No

Look up Thurston County, WA on the FEMA flood map

FEMA maps update periodically; verify zone before buying flood insurance or building.

Summary

Thurston County requires any development in a designated floodplain or flood hazard area to go through the county's Critical Areas Ordinance review process, not just standard zoning approval, per TCC 21.54.020.

These county ordinances apply to unincorporated areas of Thurston County. Incorporated cities within the county may have their own rules that take precedence over county-level regulations.

All floodplains or flood hazard areas as designated or described by the Thurston County Critical Areas Ordinance (Title 24 TCC) or the Thurston County Agricultural Activities Critical Areas Ordinance (Chapter 17.15 TCC) for agricultural activities shall be subject to the review processes, standards and conditions as specified in the applicable critical areas ordinance.

View official code

Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 77).

Full Breakdown

Thurston County Code 21.54.020 provides that all floodplains or flood hazard areas designated under the county's Critical Areas Ordinance (Title 24 TCC), or, for farmland, the Agricultural Activities Critical Areas Ordinance, Chapter 17.15 TCC, are subject to the review processes, standards, and conditions set out in that applicable critical areas ordinance rather than a separate floodplain-specific permit track. In practice this folds floodplain regulation into the same critical-areas review that covers wetlands, habitat, and aquifer recharge areas, so anyone proposing work in a mapped floodplain has to clear that review before development can proceed.

Violations & Fines

Building, filling, or grading in a mapped floodplain without going through the Title 24 critical areas review TCC 21.54.020 requires can void permits and expose the project to code enforcement action by Thurston County.

Frequently Asked Questions

Does Thurston County have its own floodplain permit process?

No separate floodplain permit exists. TCC 21.54.020 routes floodplain development into the county's Title 24 Critical Areas Ordinance review, which sets the applicable standards and conditions.

What if the floodplain property is used for farming?

Agricultural activities and facilities in floodplains follow the Agricultural Activities Critical Areas Ordinance, Chapter 17.15 TCC, instead of the general Title 24 review track.

How does the county identify flood hazard areas?

Thurston County uses FEMA Flood Insurance Rate Maps (FIRMs) to delineate the one-hundred-year floodplain referenced in its critical areas and subdivision review requirements.

Sources & Official References

Other rules in Thurston County

Flood Elevation RequirementsSome Restrictions Vehicle Idling RestrictionsSome Restrictions Boat Dock PermitsSignificant Restrictions Erosion ControlSome Restrictions Stormwater ManagementSome Restrictions Noise Ordinances: Barking DogsSome Restrictions Parking Rules: Loading ZonesSome Restrictions Parking Rules: Driveway RulesSome Restrictions Parking Rules: Abandoned VehiclesSome Restrictions Fence Regulations: Retaining WallsSome Restrictions Animal Ordinances: Cat RulesSome Restrictions

All Thurston County rules

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