Wetland rating system

Rating systems are designed to help agencies make decisions about standards for protecting wetlands, including buffers. There are two wetland rating system manuals: one for the west side of the state and one for east of the Cascade range.

Washington's wetlands vary widely in their functions and values. Some types are common while others are rare. Some are heavily disturbed while others are still relatively undisturbed. All, however, provide some valuable wetland functions and resources that are ecological, economic, recreational, or aesthetic.

To protect individual wetlands effectively, managers, planners, and citizens need tools to understand the resource value each wetland provides. The rating system was designed to differentiate between wetlands based on:

  • Sensitivity to disturbance
  • Rarity
  • Our ability to replace them
  • Functions they provide

The rating system groups wetlands into four categories.

In 2014, we updated the Washington State Wetland Rating System for both eastern and western Washington. The 2014 publications marked the third update for the rating system for eastern Washington and the fourth update for western Washington since 1991.

The 2014 rating system took effect Jan. 1, 2015. This means you're required to use the 2014 updates for projects needing our authorization. 

Applicants applying for a local permit need to consult with each specific city or county government regarding their critical areas ordinance (CAO). If a CAO contains the language “2004 rating system or as revised,” the applicant will likely need to use the 2014 updates to address local government requirements.

Some local jurisdictions may have language in their CAO that requires the use of the earlier 2004 rating systems. This means we'll keep the 2004 versions available electronically.

Version 2 of the 2014 rating system for western Washington was published in July 2023. If you have any questions about how Version 2 of the 2014 wetland rating system may affect CAO or SMP updates, email Rick Mraz, Ecology's wetland policy lead.

The rating system is primarily intended for use with vegetated, freshwater wetlands identified using the federal delineation manual and regional supplements. The rating system also categorizes estuarine wetlands but doesn't characterize their functions.

The “rating” categories are intended to be used as the basis for developing standards for protecting and managing wetlands to reduce further loss of their value.

Wetland rating can help you decide:

  • The width of buffers needed to protect the wetland from adjacent development.
  • The amount of mitigation needed to compensate for impacts to the wetland.
  • Permitted uses in the wetland.

We've developed recommendations for standards in volume two of our best available science report and wetland guidance for CAO updates.

Using the rating system for compensatory mitigation planning

The rating system doesn't replace a full assessment of wetland functions that may be necessary to plan and monitor a compensatory mitigation project.

The rating system shouldn't be used to estimate the changes in the functions of wetlands as a result of impacts or mitigation.

We've developed a separate tool to address this issue called the Credit/Debit Method.