Primary purpose
To assess wetland functions in the 404 Regulatory Program as well as other regulatory, planning, and management situations.
Expertise needed
Individuals with a minimum of an undergraduate degree in biology, wildlife management, environmental science or several years of experience in one these areas.
Applicable habitat types
All wetland types in the contiguous United States.
Categories assessed
Eleven functions and values are addressed: ground water recharge; ground water discharge; floodflow alteration; sediment stabilization; sediment/toxicant retention; nutrient removal/transformation; production export; wildlife diversity/abundance; aquatic diversity/abundance; recreation; and uniqueness/heritage. WET also provides a procedure to evaluate habitat suitability for 14 waterfowl species groups, four freshwater fish species groups, 120 species of wetland-dependent birds, and 133 species of saltwater fish and invertebrates.
Procedure
The user(s) assembles available information (e.g., soil survey, topo maps, aerial photos), selects the type of evaluation, and delineates the assessment areas. The possible types of evaluation include social significance (levels 1 or 2), effectiveness/opportunity (levels 1, 2, or 3), and habitat suitability. The user reviews the available data and/or visits the wetland and provides yes-no answers to questions. The responses to these questions are analyzed in a series of interpretation keys that assign probability ratings of high, moderate, or low to each function/value for the selected levels of evaluation.
Key Terminology
Effectiveness: the capability of a wetland to perform a function due to its physical, chemical, and biological attributes. It does not estimate the magnitude at which a function is performed, only the probability that a wetland will perform the function. (Measure provided for all functions except wildlife diversity/abundance, uniqueness/heritage, and recreation).
Functions: the physical, chemical, and biological processes or attributes of a wetland without regard to their importance to society.
Opportunity: the chance or opportunity a wetland has to perform a function. (Measure provided for only floodflow alteration, sediment/toxicant retention, and nutrient removal/transformation).
Probability rating: measure of the potential of a wetland to perform a function. It is not a direct estimate of magnitude of a function or value, rather it is an estimate of the probability that a function or value will exist or occur in a wetland to an unspecified degree.
Social significance: a nonstatistical measure of the importance society may attach to a wetland due to the official recognition of its natural features, economic value, strategic location, or other factors. (Measure provided for all functions except production export, wildlife diversity/abundance breeding, migration, and wintering).
Values: wetland processes or attributes that are valuable or beneficial to society.
Output
Rating of probability that a function or value will occur in the wetland with respect to social significance, effectiveness, and/or opportunity.
Estimated time to assess 1 acre site
Total 14-42 hours per Assessment Area (AA).
8 hours: Prepare for evaluation (step 1).
4-5 hours: Social significance (step 2)(1-2 hours for Level 1; several hours for Level 2).
2-29 hours: Effectiveness and opportunity evaluation (step 3)(1-2 hours for Level 1; 2-3 hours for Level 2; and several days for Level 3).
Comparison of habitat types
Can directly compare all wetland types within the contiguous United States.
Contact person
Paul Adamus, Adamus Resource Assessment, Inc. 6028 NW Burgundy Dr., Corvallis, OR 97330 phone: (503) 745-7092; fax: (503) 753-4507; e-mail: adamusp@ucs.orst.edu
Use as guide to design
WET should not be used as a guide to design; however, individual variables (questions) may provide useful information. For example, WET uses opportunity variables in the effectiveness interpretation keys, but does not set upper limits on those opportunities that could potentially reduce function or value (e.g., Long fetch and high exposure to waves is associated with a high probability rating for sediment stabilization). In some circumstances, a wetland may have eroded to the point that it no longer has the capacity to dissipate erosive forces. An upper limit on the opportunity must be defined to insure that the existing or planned wetland can predictably have the capacity to provide a function. Information from WET was incorporated directly into a wetland design guide (Marble 1992). That document uses WET’s information on wetland "effectiveness" to suggest features potentially useful for optimizing particular functions, and it uses WET’s information on "opportunity" for guiding site selection. As noted in the Marble (1992) introduction, this information should be used as a conceptual starting point rather than as a procedural manual (also refer to Adamus 1988). Some of the variables may provide useful information. Users can refer to the questions to determine which conditions increase or decrease function or value. This can be translated into design criteria with explicit measurements (e.g., design a wetland with no outlet). Finally, the design criteria for some variables may be unsuitable and the overall rating of function/value may be misleading for the reasons given above.
Related procedures
Three procedures are based upon WET, but are modified and adapted to local conditions. WEM (USCOE 1988a) is adapted to the North Central United States, and the VIMS Method (Bradshaw 1991) is adapted to non-tidal wetlands of Virginia. WET-BLH (Adamus et al. 1990) is adapted to bottomland hardwoods (BLH) in the southeastern United States.
Extent of use/field testing
WET has been applied to primarily large projects (e.g., highways), a few routine regulatory actions, and some restore/created wetlands. The extent of use over the last two years is unknown.
Proposed future revisions
None.
Key References
Adamus, P.R., E.J. Clairain, R.D. Smith, and R.E. Young. 1987. Wetland Evaluation Technique (WET), Volume II: Methodology. Department of the Army, Waterways Experiment Station, Vicksburg, MS. NTIS No. ADA 189968.
Adamus, P.R., L.T. Stockwell, E.J. Clairain, M.E. Morrow, L.D. Rozas, and R.D. Smith. 1991. Wetland Evaluation Technique (WET), Volume I; Literature Review and Evaluation Rationale. Technical Report WRP-DE-2, U.S. Department of the Army, Waterways Experiment Station, Vicksburg, Mississippi. 287 pp.
Additional references
Adamus, P.R. 1988. Criteria for created or restored wetlands. Pages 369-372 In D.D. Hook et al. (eds.). The Ecology and Management of Wetlands. Vol 2: Management, Use and Value of Wetlands. London & Sydney: Croom Helm.
Adamus, P.R., R.D. Smith, and T. Muir. 1990. Manual for Assessment of Bottomland Hardwood Functions. EPA 600/3-90/053. Prepared by U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS.
Marble, A. 1992. A Guide to Wetland Functional Design. Lewis Publishers, Chelsea, MI. 222 pp.
U.S. Army Corps of Engineers. 1988a. The Minnesota Wetland Evalution Methodology for the North Central United States. U.S. Army Corps of Engineers, St. Paul District, St. Paul, MN.