Primary purpose
To assess wetland functions in conjunction with conducting an inventory of non-tidal wetlands in Virginia.
Expertise needed
Professional(s) with schooling in environmental sciences.
Applicable habitat types
Non-tidal wetlands in Virginia’s coastal plain.
Categories assessed
Eight functions are addressed: flood storage and storm flow modification, nutrient retention and transformation, sediment and toxicant trapping, sediment stabilization, wildlife habitat, aquatic habitat, public use, and other factors.
Procedure
The user(s) visits a wetland and completes data sheets for each function that (a) identify factors, (b) list conditions for each factor, (c) assign a rating (i.e., high, moderate, or low) to each condition, and (d) provides an interpretation key. The interpretation key uses a combination of the factor ratings to produce a probability rating (high, moderate, or low) for each function.
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 (Adamus et al. 1987).
Factor: determine a wetland’s ability to perform a function.
Opportunity: the chance or opportunity a wetland has to perform a function (Adamus et al. 1987).
Probability rating: measure of the potential of a wetland having opportunity and effectiveness at performing a function.
Output
Rating of probability that a function will occur in the wetland with respect to opportunity and/or effectiveness.
Estimate time to assess 1 acre site
Total 4 hours per site.
Time variable: Prepare for evaluation (step 1)
4 hours: Evaluate wetland (step 2) and complete summary sheet (step 3).
Comparison of habitat types
Can directly compare non-tidal wetlands within Virginia’s coastal plain.
Use as guide to design
The VIMS Method models should not be used as a guide to design; however, individual variables (factors) may provide useful information. It is not the intended purpose for the procedure; therefore, it contains properties that limit its application for this purpose. For example, the VIMS Method uses opportunity variables, but does not set upper limits on those opportunities that could potentially reduce function (e.g., high erosive conditions 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. Also, the VIMS Method does not provide validated threshold values for many variables. Some of the variables may provide useful information. Users can refer to the questions to determine which conditions increase or decrease function. This can be translated into design criteria with explicit measurements (e.g., design so the wetland stores >25% of two-year, 24hr storm; Factor 1). Finally, the design criteria for some variables may be unsuitable and the overall rating of function may be misleading for the reasons given above.
Contact person
Carl Herschner, Virginia Institute of Marine Science (VIMS), P.O. Box 1346, Gloucester Point, VA. 23062 phone: (804) 684-7387; fax: (804) 684-7179; e-mail: carl@vims.edu
Related procedures
The introduction states that portions of the WET-BLH (Adamus et al. 1990) and CT Method (Ammann et al. 1986) were incorporated extensively.
Extent of use/field testing
The VIMS Method has been used most extensively by VIMS in their inventory and research efforts (estimated fifty times over the last two years). It also has been used on several routine regulatory projects (Pers. comm.: Julie Bradshaw, VIMS, June 30, 1998).
Proposed future revisions
None.
Key Reference
Bradshaw, J.G. 1991. A Technique for the Functional Assessment of Nontidal Wetlands in the Coastal Plain of Virginia. Special Report No. 315 in Applied Marine Science and Ocean Engineering. Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, VA.
Additional Reference
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.