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Critical Areas

This page provides an overview of the critical areas regulations required of all cities, towns, and counties in Washington State under the Growth Management Act.


The Growth Management Act (GMA) requires all cities and counties in Washington to adopt regulations protecting “critical areas” in order to preserve the natural environment, wildlife habitats, and sources of fresh drinking water. Critical areas regulation also encourage public safety by limiting development in areas prone to natural hazards like floods and landslides.

RCW 36.70A.030(6) defines five types of critical areas:

  • Wetlands
  • Areas with a critical recharging effect on aquifers used for potable water
  • Fish and wildlife habitat conservation areas
  • Frequently flooded areas
  • Geologically hazardous areas

RCW 36.70A.030(6) also notes the following:

"Fish and wildlife conservation areas" does not include such artificial features or constructs as irrigation delivery systems, irrigation infrastructure, irrigation canals, or drainage ditches that lie within the boundaries of and are maintained by a port district or an irrigation district or company.

Counties and cities are required to develop policies and development regulations to protect the functions and values of critical areas using the best available science (RCW 36.70A.172). All jurisdictions are required to review, evaluate, and, if necessary, revise their critical areas ordinances according to an update schedule. For more information on the schedule and required updates, see our page on the Comprehensive Plan Update Process.

The Washington State Department of Commerce provides many resources for creating an effective critical areas ordinance. The handbook and guidebook below provide a great overview of critical areas issues, as well as detailed guidance for each step in the process (from designating critical areas to specific protection methods and monitoring).

Local governments can take certain actions to create flexibility in their critical areas regulation. For information on exemptions and exceptions to critical areas regulation, see our page on Flexibility in Environmental Regulation.

Note: The Department of Ecology has completed their 2022 update of the Wetland Guidance for Critical Areas Ordinance (CAO) Updates, which includes the 2018 critical areas guidance changes for wetland buffers and more. For more information and to access the publication, see their Local Wetland Regulations page.

Best Available Science

GMA requires local governments to use the best available science (BAS) when reviewing and revising their critical areas policies and regulations (RCW 36.70A.172).

Jurisdictions must demonstrate that the best available science has been considered when creating their critical areas ordinance by documenting scientific sources that support their approach to regulating critical areas and explaining when policies depart from science-based recommendations. Chapter 365-195 of the Washington Administrative Code (WAC) serves as a guide for establishing what is considered the best available science.

The Department of Commerce, Growth Management Services, and the Department of Ecology provide helpful guidance on addressing the GMA's best available science requirements. See resources below.

Examples of BAS Reviews

Below are examples from local governments in Washington State that provide best available science review references and/or reports.

Critical Areas Update Process

Critical Areas Ordinances must be evaluated and, if needed, revised every eight years per the schedule provided in RCW 36.70A.130. In 2022, the eight-year comprehensive plan periodic update cycle was extended to a 10-year cycle after the upcoming cycle. MRSC’s page on the Comprehensive Plan Update Process outlines the process and timeline for these updates in greater detail.

The Washington Department of Commerce publishes a Critical Areas Checklist to help local governments update their critical areas ordinance and development regulations.


Examples of Critical Areas Ordinances

Below are examples of city and county critical area ordinances from Washington State, along with a small selection of other states.



Other States

  • Baltimore County, MD Chesapeake Bay Critical Area Article 33 – Establishes a resource protection program in the Chesapeake Bay Critical Area that addresses water quality, fish and wildlife, and land use in similar fashion to Washington critical area definitions
  • San Diego, CA Code Ch. 14 Art. 3 Div. 1 – Contains regulations for environmentally sensitive lands similar to Washington critical areas such as sensitive biological resources, steep hillsides, coastal beaches, sensitive coastal bluffs, floodplains
  • St. Helens, OR Ch. 17.40 – Establishes protective measures for several environmentally sensitive areas relevant to Washington critical areas including wetlands and riparian areas
  • Sitka, AK Code Title 20 – Assures the maximum practicable safety for residents given the topographical characteristics and meteorological conditions, and establishes land use regulations for two environmentally critical areas: floodplain management and coastal management

Voluntary Stewardship Program

The Voluntary Stewardship Program (VSP) was created in 2011 and allows participating counties to develop local work plans that use voluntary and incentive-based tools, as an alternative to regulation, to protect critical areas and agricultural lands (see RCW 36.70A.710).

For more information and examples of programs, see the "Voluntary Stewardship Plans" section of our Flexibility in Environmental Regulation page.

Legal References

Court Decisions

This section contains a selected list of court decisions about critical areas and the Growth Management Act.

Agricultural Land

Clallam County v. W. Washington Growth Mgmt. Hearings Board, 130 Wn. App. 127 (2005), review denied, 163 Wn.2d 1053 (2008) – The court concluded that preexisting agricultural uses are not exempt from all critical areas regulation. The court also held that the county was not limited to exempting only designated agricultural resource land from full critical areas regulation and that it may expand its exempt agricultural land to meet its local conditions. However, the county must balance such expanded exemption with corresponding restrictions that take into account the specific harms threatened by the expanded class of farm lands.

Best Available Science

Whidbey Environmental Action Network v. Island County, 14 Wash. App.2d 514 (2020) This matter concerned whether Island County’s critical areas ordinance provided proper protection of the western toad, identified by the Department of Fish and Wildlife as a “candidate” and “priority” species whose priority area is “any” occurrence. Whidbey Environmental Action Network (WEAN) claimed the ordinance failed to properly designate upland occurrences of the western toad and that it gave too much discretion to the planning director to waive the requirement for a biological site assessment when development is located within 1,000 feet of habitat for protected species or a conservation area or buffer. The Court of Appeals, Division 2, agreed that the County’s limited protection of “any occurrence” to only those occurrences that have been documented as of the date of ordinance adoption is contrary to the best available science in the WAC; the ordinance should provide for automatic designation of upland occurrences of the western toad when identified. The court also agreed that the authority given to the planning director to waive a biological site assessment is contrary to law because it gives the director nearly unfettered discretion, with no restrictions. This is contrary to the GMA because it does not ensure adequate protection of critical areas and contrary to the WAC, which requires a precautionary approach when waiving requirements that protect critical areas.

Ferry Cty. v. Growth Mgmt. Hearings Bd., 184 Wn. App. 685 (2014) – The Department of Fish and Wildlife recommended 31 species for consideration for local importance designation in Ferry County. The county did not designate any species of local importance or areas for fish and wildlife conservation. The hearings board decided that Ferry County’s Critical Areas Ordinance was non-compliant with the GMA because it failed utilize the best available science (BAS) or provide a reasoned explanation for deviating from BAS to designate species of local importance or fish and wildlife conservation areas. The superior court ruled in favor of the county, but upon appeal the hearing board decision was reinstated. The court found that the county failed to use BAS and the reasoning provided for their ordinance was unsubstantiated.

Yakima County v. E. Wash. Growth Mgmt. Hearings Bd., 168 Wn. App. 680 (2012) – The hearings board decided that the county's standard stream buffers were unsupported by the best available science, and that the minimum adjustments allowed to be made to stream and wetland buffers failed to comply with the GMA. The court of appeals held that the superior court erroneously reversed the hearings board's decision on stream buffer widths, noting that the record did not show the county systematically analyzed the efficacy of the stream buffers in place since 1995, or that “for the most part” these buffers had adequately performed their intended function. However, the court of appeals ruled that the superior court properly reversed the hearings board's decision to invalidate the county's decision not to designate and regulate type 5 ephemeral streams under the county's critical areas ordinance. The court determined that the county provided a reasoned justification in deciding not to designate or regulate ephemeral streams as critical areas.

Olympic Stewardship Found. v. W. Wash. Growth Mgmt., 166 Wn. App. 172 (2012), review denied, 174 Wn.2d 1007 (2012) – Olympic Stewardship Foundation challenged the county's vegetation regulations applicable to rivers subject to channel migration, arguing that the regulations violated the GMA's "best available science" requirement and that the Legislature's 2010 amendment to RCW 36.70A.480 invalidates the county's nonconforming use regulation for critical areas. The court held there was no duty on a county to describe each step of the deliberative process that links the science that it considers to the adopted policy or regulation; rather, the county must address on the record the relevant sources of best available scientific information included in the decision-making. The court also found that, by prohibiting vegetation removal and development only within those areas determined to be "high risk" critical areas, any dedications of land within the critical areas are de facto "reasonably necessary as a direct result of the proposed developments," in compliance with RCW 82.02.020.

Stevens County v. Futurewise, 146 Wn. App. 493 (2008), review denied, 165 Wn.2d 1038 (2009) – The court held that substantial evidence supported the growth board's decision that the county's critical habitat code provisions did not comply with the GMA, because the county failed to designate all critical habitats and failed to consider the best available science in designating critical habitats, as required by RCW 36.70A.172(1). The county had to use some kind of scientific methodology in a reasoned process of analysis to designate the habitats.

"No Harm" Standard

Swinomish Indian Tribal Community. v. W. Washington Growth Mgmt. Hearings Board, 161 Wn.2d 415 (2007) – The tribe challenged the county's critical areas ordinance alleging, among other things, that a "no harm" provision failed to protect critical areas, as required by RCW 36.70A.060(2). The court concluded that the "no harm" standard protected critical areas by maintaining existing conditions. The GMA does not impose a duty on local governments to enhance critical areas. The county did not need to require buffers near rivers, where previously existing buffers had long since been removed (there is no requirement to enhance). The court also concluded that, while best available science needed to be considered and included in its record, the county did not need to follow it. A county may depart from the best available science if it provides a reasoned justification for doing so.

Public Health and Safety Considerations

Futurewise v. Snohomish County, 9 Wn.App.2d 391 (2019) – Following the Oso landslide, the county updated its regulations designating and protecting critical areas, including geologically hazardous areas. Futurewise appealed to the Growth Management Hearings Board, arguing that the county’s regulations failed to adequately protect the public health and safety from geologically hazardous areas as required by the Growth Management Act. The Hearings Board concluded that the regulations met a majority of the Growth Management requirements. Futurewise appealed and the court of appeals affirmed finding that the Growth Management Act does not require the county to consider public health and safety when developing critical area regulations.
Local government must adopt regulations to protect critical areas. They must use best available science in developing their regulations. But there is no requirement that they consider public health and safety when developing critical area regulations. The statutes require the protection of critical areas and not anything external to the critical areas, such as public health and safety.

Shoreline Master Plan Updates

KAPO v. Central Puget Sound Growth Mgmt. Hearings Board, 160 Wn. App. 250 (2011) – Following 2010 amendments to RCW 36.70A.480 that applied retroactively, the court held that the GMA was to regulate critical areas in shoreline areas until such time as Shoreline Management Act plans are updated.


Stevens County v. E. Wash. Growth Mgmt. Hearings Bd., 163 Wn. App. 680 (2011), review denied, 173 Wn.2d 1019 (2012) – The court concluded that the county subdivision code failed to protect critical areas, as required by the GMA. Significantly, the code did not address impervious surface coverage in multiple important contexts, it did not apply county-wide, and it did not mention methods for addressing storm water or impervious surface coverage.

Recommended Resources

Several state agencies provide a number of resources specific to each type of critical area. See the links below for more information.


Critical Aquifers Recharge Areas

Fish and Wildlife Habitat Conservation Areas

Frequently Flooded Areas

Geologically Hazardous Areas

Last Modified: March 04, 2024