Wetlands function assessment project

The Wetlands Function Assessment Project provides the scientific basis for our current wetland rating system. Developed between 1996-2001, the methods assess how well a wetland improves water quality, reduces flooding, provides wildlife habitat, and performs other wetland functions. We coordinated the project with funds from EPA.

The documents are provided here for historical reference to those wishing to explore the scientific basis for the wetland rating systems, which is the current tool for gathering general information on functions provided by wetlands.

Methods based on wetland classifications, regions

Methods for assessing wetland functions, commonly called the Washington State Wetland Function Assessment Methods, are a collection of assessment methods developed by an interdisciplinary team of experts. The assessments provide a score for the degree to which several functions, up to 15, are performed by a wetland.

The methods are based on the hydrogeomorphic classification for wetlands, which categorizes wetlands into groups that function in similar ways, based on geomorphic and hydrologic characteristics. The highest categories or classes for wetlands in a region are defined nationally. Sub-classes for each class are defined regionally by experts within that area. In Washington, regions were created to reflect the differences in wetland functions, or differences in how functions are performed.

HGM Classes

Riverine
Depressional
Slope
Lacustrine fringe
Estuarine fringe
Flats (mineral and organic)

Regions in Washington

Montane
Lowlands of Western Washington
Columbia Basin
Lowlands of Eastern Washington

 

Methods for assessing wetland functions were completed for hydrogeomorphic classes/sub-classes in two regions in Washington: Lowlands of Western Washington (riverine and depressional wetlands) and the Columbia Basin (depressional wetlands). The methods can be downloaded below.

Lowlands of Western Washington

  • Part 1: Background information and three assessment methods, one each for four types of depressional wetlands occurring in the lowlands of Western Washington (depressional closed, depressional outflow, riverine flow-through, riverine impounding).
  • Part 2: Procedures and field forms for collecting and recording the data needed to apply the methods.

Columbia Basin methods

  • Part 1: Background information and three assessment methods, one each for three types of depressional wetlands occurring in the Columbia Basin (alkali, freshwater-short duration, and freshwater-long duration).

  • Part 2: Procedures and field forms for collecting and recording the data needed to apply the methods.

Current applicability of the methods

We highly recommend that those who apply the methods do so only after attending a five-day training session.

Training is important to properly interpret and apply the methods, especially when collecting data in the field. Training is also important so results are accurate, consistent, and reproducible.

Note: The documents are provided here for historical reference to those wishing to explore the scientific basis for the wetland rating system, which is the current tool for gathering general information on the functions wetlands provide. We have been unable to offer training on the methods in more than a decade, and do not have plans to offer training in the foreseeable future. Therefore we can no longer support its use to assess functions of wetlands.