Local wetland regulations: Growth Management Act technical assistance

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

The 1990 state Growth Management Act (GMA) requires local governments to include the 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 Legislature.

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

As part of this effort, we review the wetland chapters of draft CAOs, meet with local planning staff and consultants, and provide wetlands presentations to advisory groups, planning commissions, and local elected officials.


Our overall guidance, called Wetland Guidance for CAO Updates, describes the important topics that should be addressed in the wetlands section of a critical areas ordinance (CAO). Our guidance includes a version for Eastern Washington and another for Western Washington.

Both include 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.

This guidance 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 Systems: The rating systems for Eastern and Western Washington are 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 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 wetlands 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 characterize 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): This document 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 in regarding wetland mitigation. Part 2 contains technical information for developing wetland mitigation plans and proposals.

July 2018 modified habitat score ranges

We have modified the habitat score ranges we use in our wetland buffer tables. As a result, we have updated sections XX.040 and XX.050 in our wetland CAO guidance. These updated sections are available below: For more information on the modifications, see our frequently asked questions.