Local wetland regulations: Growth Management Act technical assistance

We assist local governments in their efforts to use best available science to adopt regulations that protect wetlands and their functions.

The state Growth Management Act (GMA) requires local governments to include best available science in developing policies and regulations protecting the functions and values of critical areas. All Washington counties and cities are required to review, evaluate, and, if necessary, revise their critical areas ordinances (CAO) according to a schedule established by the Washington State Legislature.

For more GMA information including updated resources, grants, and checklists, please refer to the Department of Commerce's Growth Management Services.

As part of our efforts to assist local governments, we review the wetland chapters of draft CAOs, meet with local planning staff and consultants, and provide wetland presentations to advisory groups, planning commissions, and local elected officials.

Our overall guidance, updated in 2022, is called Wetland Guidance for Critical Areas Ordinance (CAO) Updates: Western and Eastern Washington. It describes the important topics that should be addressed in the wetland section of a CAO. 

The guidance includes recommendations for wetland protection based on best available science, such as wetland buffers and mitigation options. The guidance also includes a sample chapter for wetlands that incorporates these recommendations into a format similar to many local CAOs and contains definitions commonly used in wetlands regulations.

The 2022 guidance updates the following 2016 versions of the guidance:

It also revises the wetland-specific provisions in the Department of Commerce's Critical Areas Assistance Handbook. For assistance with other aspects of a critical areas ordinance update, please contact the Department of Commerce's Growth Management Services.

The Voluntary Stewardship Program (VSP) provides an alternative incentive-based approach for counties to address two fundamental goals of the state Growth Management Act:

Protect and enhance critical areas within the area where agricultural activities are conducted, while maintaining and improving the long-term viability of agriculture in the state of Washington and reducing the conversion of farmland to other uses - RCW 36.70A.700

We are interested in helping VSP watersheds achieve compliance with clean water requirements, and protect and restore critical areas. As members of the State-level VSP Technical Panel, we attend regular meetings and review periodic reports submitted by participating counties.

The publications listed below can be used by cities and counties to help develop regulations for protecting and managing wetlands:

  • Washington State Wetland Rating System: The wetland rating system is designed to differentiate between wetlands based on their sensitivity to disturbance, their significance, their rarity, the ability to replace them, and the functions they provide. Wetlands are grouped into four categories used to determine regulatory criteria for avoidance, width of buffers, and compensatory mitigation ratios.
  • Wetlands in Washington State - Volume 1: A Synthesis of the Science (March 2005): Under the Growth Management Act, local governments are required to use the best available science when reviewing and revising their wetland policies and regulations. We worked with the Washington Department of Fish and Wildlife to develop this comprehensive synthesis of the science regarding freshwater wetlands to assist local governments.
  • Wetlands in Washington State – Volume 2: Guidance for Protecting and Managing Wetlands (April 2005): This volume translates the science synthesized in Volume 1 into guidance on protecting and managing wetlands for local governments.
  • Characterizing Wetland Buffers (September 2017): This manual provides procedures to assess compliance with wetland buffers that are required under regulations both at the state and local levels. It can be used by state agencies and local governments to characterize both the implementation and the effectiveness of their requirements for wetland buffers. The results can also be used to inform management decisions on policies and regulations regarding buffers.
  • Interagency Guidance on Wetland Mitigation in Washington, Parts 1 and 2 (March 2006, Part 1 updated April 2021): This interagency guidance compiles existing information on wetland mitigation, including current agency policies. Part 1 provides an overview of the role the agencies play in regulating wetlands and explains some of the factors that go into permitting decisions regarding wetland mitigation. Part 2 contains technical information for developing wetland mitigation plans and proposals.

July 2018 modified habitat score ranges for 2016 versions of our CAO guidance

We modified the habitat score ranges used in our 2016 wetland buffer tables. As a result, we updated sections XX.040 and XX.050 in our 2016 wetland CAO guidance. These updated sections are available below:

These modifications were incorporated into the 2022 guidance. For more information on the 2018 modifications, see our frequently asked questions.