Primary purpose
To assess functions at individual wetlands. Developed specifically to meet regulatory and nonregulatory needs within the existing management framework of Washington state.
Expertise needed
Technical wetland experts and those with a strong background in wetlands science. These individuals should be trained in WAFAM.
Applicable habitat types
Vegetated riverine (flow-through and impounding) and depressional (outflow and closed) wetlands in the lowlands of western Washington. Models are also being developed for three subclasses of depressional wetlands in the Columbia Basin.
Categories assessed
Fifteen functions are addressed: potential for removing sediment, potential for removing nutrients, potential for removing metals and toxic organics, potential for reducing peak flows, potential for decreasing downstream erosion, potential for recharging groundwater, general habitat suitability, habitat suitability for invertebrates, habitat suitability for amphibians, habitat suitability for anadromous fish, habitat suitability for resident fish, habitat suitability for birds, habitat suitability for aquatic mammals, habitat for native plant associations, and potential for primary production and organic export. (Note: each function is not applicable to every wetland subclass.)
Procedure
There are two main phases: development and application. During the development phase an interdisciplinary team of experts (A-Team) develops models for assessing functions of wetlands in a regional subclass. The A-Team first prepares rough drafts of the models. Models are refined through technical expert review, workshops, collecting field data at reference wetlands, calibrating models to reference wetlands, public review, and field testing. The application phase consists of applying the models to an actual project. The user(s) visits an assessment unit (AU) and completes data sheets by recording estimates/scores/ratings that best describe the listed data (e.g., landscape, water regime, vegetation, special habitat features, soils, and physical structure). Then, the user calculates the indices of potential performance and habitat suitability by (a) inputting data into a spreadsheet program or (b) applying the models for each function. The models (a) identify the variables for each function, (b) lists description of scaling for each variable, (c) assign an index (scale 0-1.0) to each description of scaling, and (d) include the equations for calculating the index of potential performance or habitat suitability. Directions are also provided for determining a qualitative rating of opportunity for many functions.
Contact persons
Thomas Hruby, Washington State Department of Ecology, P.O. Box 47690, Olympia, WA 98504-7690 phone: (360) 407-7274; fax: (360) 407-6535; e-mail: thru461@ecy.wa.gov
Teri Granger, Washington State Department of Ecology, P.O. Box 47600, Olympia, WA 98504-7600 phone: (360) 407-6547; fax: (360) 407-6535; e-mail: tgra461@ecy.gov information also available at Web site:www.wa.gov/ecology/sea/shorelan.html
Key Terminology
Functions: physical, chemical, and biological processes or attributes that contribute to the self-maintenance of wetland ecosystems (Brinson 1993), or simply, the things that wetlands do (Smith et al. 1995).
Indicators: easily observed characteristics that are correlated with a quantitative or qualitative measure of an environmental variable.
Index for habitat suitability: a numeric score indicating a wetland’s habitat suitability for a specific group of organisms (e.g., aquatic birds) relative to other wetlands within a regional wetland subclass.
Index of potential performance: a numeric score indicating a wetland’s level of potential performance for a function relative to other wetlands within a regional wetland subclass.
Level of performance: level at which a wetland area performs a function.
Opportunity: the opportunity that a wetland has to actually perform a function.
Performance score: score for a function that is calculated to factor in the size of the assessment unit (Performance score = Index of performance X size of assessment unit).
Potential: capability of a wetland to perform a function based on its environmental characteristics, i.e., the site specific conditions that indicate a wetland has the potential for performing a function.
Reduced performance: variables that are correlated with a reduction in the performance of a function; included as fractional multipliers in the models.
Reference domain: all wetlands within a defined geographic region that belong to a single hydrogeomorphic subclass.
Reference standard wetlands: sites within the reference data set, which establish the characteristics needed to be present in a wetland for it to score the highest for a function. Reference standard wetlands are those reference wetlands within a subclass and domain that are judged by an assessment team to perform at the highest level for individual functions, regardless of level of alteration.
Reference wetlands: group of wetlands within the reference domain that encompass the known variation of a hydrogeomorphic subclass. They are used to establish the range of performance within the subclass.
Suitability score: score for habitat suitability that is calculated to factor in the size of the assessment unit (Suitability score = Index for habitat suitability X size of assessment unit).
Variables: environmental characteristics that are considered to be important in the performance of a function.
Output
Measures of potential performance (or habitat suitability), and qualitative rating of opportunity for a site relative to wetlands from the same regional wetland subclass.
Estimated time to assess 1 acre site
Total 2-4 hours per assessment unit (AU) (if models are available)
2-4 hours: Read methods and procedures (step 1), gather site information (step 2), review information and make preliminary observations (step 3), visit wetland and identify approximate boundary (step 4), classify AUs (step 5), identify assess AUs based on other factors (step 6), collect field data (step 7), complete data form (step 8), calculate indices (step 9), calculate performance/suitability scores and determine opportunity (step 10), and complete summary table (step 11).
Total 2402-2404 hours (if models must be developed)
2402-2404 [15 months of work]: Development phase (prior to steps 1-3).
2-4 hours per AU: (see steps 1-11 above).
Comparison of habitat types
Can directly compare wetlands within the same regional subclass (e.g., depressional closed wetlands in the lowlands of western Washington). Cannot directly compare wetlands from different subclasses (e.g., depressional closed and depressional flow-through wetlands within same region) or different regions. However, results from assessing different regional subclasses can be used to aid in decisions.
Use as guide to design
The WAFAM assessment models can be used as a guides to design. Users can refer to the model variables to determine which conditions increase or decrease potential performance or habitat suitability. Potential performance for removing nutrients can be increased when non-clay mineral soils are >50% of the area (variable Vsorp). Each variable provides information on conditions that should be avoided. For example, to have a capacity to remove nutrients, the outlet should not be unrestricted (variable Vout). Also, the information in the WAFAM models is useful because it provides design criteria with explicit measurements (e.g., non-clay mineral soils are <50% of area).
Related procedures
WAFAM incorporates concepts and terminology of the HGM Approach (Smith et al. 1995) and IVA (Hruby et al. 1995). WAFAM differs from the HGM Approach in the following ways. For a more detailed comparison refer to Hruby et al. (1998).
• Terminology
• WAFAM provides a qualitative rating of opportunity for many functions.
• Criteria for choosing reference standard sites. The HGM Approach requires that reference standard sites be natural or relatively undisturbed, and self-sustaining. WAFAM reference standard sites are wetlands that perform at the highest level, regardless of their level of alteration.
• Approach to normalizing model equations (see discussion in Hruby et al. 1998)
Extent of use/field testing
The assessment team and field teams collected data at 88 references sites on 60 different environmental characteristics during 1997. Data collected was then used calibrate the models. Testing of the calibrated models was conducted during summer/fall 1998 by approximately 40 individuals.
Proposed future revisions
Not yet scheduled.
Key References
Hruby, T., T. Granger, K. Brunner, S. Cooke, K. Dublanica, R. Gersib, L. Reinelt, K. Richter, D. Sheldon, A. Wald, and F. Weinmann. 1998. Methods for Assessing Wetland Functions. Volume I: Riverine and Depressional Wetlands in the Lowlands of Western Washington. WA State Department Ecology Publication #98-106, July 1998. 455 pp. + appen.
Hruby, T. and T. Granger. 1998. Methods for Assessing Wetland Functions. Volume II: Procedures for Collecting data in the Lowlands of Western Washington. Washington State Department of Ecology Publication #98-107. 51 pp. + Appendices.