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2014 Updates to the Washington State Wetland Rating Systems

Ecology has updated the Washington State Wetland Rating Systems for eastern and western Washington that were published in 2004 and annotated in 2006. The categorization and scoring in the 2014 updates were calibrated at 211 wetland sites that we use as a reference. Both updates were reviewed by peers outside of Ecology and by the public. The 2014 publications are the third update of the rating system for eastern Washington and the fourth update for the western Washington version since they were first published in 1991.

The effective date of the 2014 rating systems is January 1, 2015. The January 1, 2015, effective date means that if you rate a wetland on or after that date, you will be required to use the 2014 updates for projects needing Ecology authorization. An applicant applying for a local permit will need to consult with that specific local government if its critical areas ordinance (CAO) requires the use of the rating system. If a CAO contains the language “2004 rating system or as revised,” it is likely that an applicant will need to use the 2014 updates, as of January 1, 2015, to address local government requirements.

Why did we update the rating systems?

The need to update the rating systems published a decade ago has become apparent as we continue to expand our understanding of how wetlands function and what is needed to protect them. By updating the rating systems, we hope to provide a more accurate characterization of the functions performed by individual wetlands: one that is based on the most recent science.

In these updates, we kept:

  • The four categories of wetlands (Category I, II, III, IV)
  • The three functions that are rated (Improving Water Quality, Hydrologic Functions, Habitat Functions)
  • About two-thirds of the questions found on the field forms in the 2004 versions.

What changed?

The substantive differences between the 2004 versions and the draft updates are:

  1. Changing the scale of scores from 1 – 100 to 9 -27 to better reflect the scientific accuracy of the tools (see below for score conversion tables).
  2. Starting with a qualitative rating of High, Medium, or Low for different aspects of functions before assigning a score to them.
  3. Keeping the questions for the Site Potential found in the 2004 versions, but replacing the Opportunity section with two new sections called Landscape Potential and Value.

The new sections on Landscape Potential and Value were developed as part of the Credit-Debit Method (Calculating Credits and Debits for Compensatory Mitigation in Wetlands) developed by Ecology in 2012. The Credit-Debit Method underwent peer and public review and was field tested for one year prior to publication in 2012.

Other changes include:

  1. The addition of interdunal wetlands with very high habitat scores to the list of Category I wetlands. This is based on our field work during the last decade on barrier beaches along the coast. In the 2004 version, all interdunal wetlands were categorized only as Category II and III.
  2. The addition of calcareous fens to Category I peat wetlands in eastern Washington. These peat systems are extremely rare in the state and sensitive to disturbance. As of 2014 only five calcareous fens have been found in the Okanogan region by the Natural Heritage Program at the Department of Natural Resources.
  3. Incorporating the annotations that were added in 2006 directly into the text.
  4. Including current definitions used by the Washington State Department of Fish and Wildlife for Priority Habitats and by the Natural Heritage Program at the Department of Natural Resources for Natural Heritage Wetlands. These wetlands are now called Wetlands of High Conservation Value.

June 2014 Webinar on Updated Rating Systems and Wetland Buffer Guidance

On June 3, 2014, Ecology wetland staff hosted a one-hour webinar on Ecology’s 2014 updates to the wetland rating systems and how they apply to Ecology’s wetland buffer guidance. Additional information about integrating the rating system updates into Critical Areas Ordinance (CAO) updates was also provided.

> View Presentation only (PDF)
> Listen to Recorded Audio version (YouTube)

Download the 2014 Rating Systems and Forms

How do the changes affect Ecology’s guidance on buffers?

Ecology is not changing the recommended buffer widths found in the following documents:

Ecology's recommendations for buffers are based in part on the category of the wetland and the scores for functions. The update of the rating systems keeps the same four wetland categories, but the scale of scores has been adjusted.  Therefore, any buffer guidance in CAOs or SMPs based on scores for functions needs to be adjusted to reflect the new range of scores (for example, in the 2004 version the medium score range for habitat was 20-28 and it is now 5-7).   See below for score conversion tables.

Many local jurisdictions have included language on buffers in their critical areas ordinances based on Ecology's buffer guidance. For the 2015-2019 critical areas ordinance update cycle, we are not proposing any changes to the recommended buffer widths, however, any buffer strategy that uses function scores to determine buffer widths will need to be adjusted to use the new scores. For more information, contact Donna Bunten at or 360-407-7172.

Converting scores for categories and function scores between the 2004 and 2014 rating systems

For those jurisdictions that have adopted Alternative 3 or 3A from Appendices 8-C or 8-D in the 2005 guidance, or Table XX.1 from the guidance for small cities (Publications 10-06-001 and 10-06-002), we have modified the appendices and Table XX.1 to incorporate the 2014 score range:

You can also compare the old and new score ranges in the tables below. (Note: The tables below can be used to adjust the scores in Tables 3, 4, 5a, 5b, 6a, and 6b in the mitigation guidance.)

Tables for converting category scores

2004 Western WA 2014   2004 Eastern WA 2014
> 70 Category I 23-27   > 70 Category I 22-27
51-69 Category II 20-22   51-69 Category II 19-21
30-50 Category III 16-19   30-50 Category III 16-18
<30 Category IV 9-15   <30 Category IV 9-15

Tables for converting function scores

2004 Final Habitat Score 2014   2004 Final Water Quality Score 2014
29-36 High 8-9   24-32 High 8-9
20-28 Medium 5-7        
< 19 Low 3-4        

More information

For more information, contact:


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