Primary purpose
To assess wetland functions and determine whether a planned wetland has been adequately designed to achieve defined function goals. EPW can also be used in other regulatory, planning, and management situations.
Expertise needed
Professional(s) who have training and experience in wetland science.
Applicable habitat types
All wetlands types in the United States.
Categories assessed
Six functions are addressed: shoreline bank erosion control; sediment stabilization; water quality; wildlife; fish; and uniqueness/heritage.
Procedure
The user(s) visits a wetland area (or reviews plans for predicted future conditions) and completes data sheets that (a) identify the individual model elements, (b) list conditions of model elements, (c) assign a score (scale 0-1.0) to conditions for each element, and (d) include the model for calculating the functional capacity index (FCI). Functional capacity units (FCUs) for each function are also calculated by multiplying the applicable area by the FCI score. The results are then analyzed.
Key Terminology
Element: a physical, chemical, or biological characteristic of the wetland or landscape that dominates the wetland’s capacity to perform a function.
Functional capacity: the magnitude to which an area of wetland performs a function. Functional capacity is dictated by attributes of the wetland ecosystem and the surrounding landscape and interaction between the two.
Functional capacity index (FCI): an index of the capacity of a wetland to perform a function relative to other wetlands within a wetland class. (1.0 = optimal functional capacity; 0 = no functional capacity).
Functional capacity units (FCUs): measure of functional capacity incorporating size of the wetland area (FCU = FCI x size of wetland assessment area).
Planned wetland: design or an implemented design for a constructed, restored, or enhanced wetland.
Output
Measure of functional capacity of a site.
Estimated time to assess 1 acre site
Time variable: Define scope of evaluation (step 1) and characterize WAA (step 2).
1-2 hours: Assess WAA (step 3).
Comparison of habitat types
Can directly compare wetlands within same the wetland class (e.g., tidal). Cannot directly compare wetlands from different classes (e.g., tidal and non-tidal stream/river), although the results from assessing different wetland types can be used to aid in decisions.
Use as guide to design
EPW may be used as a guide to design. Users can refer to the variables (elements) to determine which conditions increase or decrease functional capacity. Functional capacity for sediment stabilization is increased when the wetland is designed to have percent plant cover of >75% (element 10b). Each variable provides information on conditions that should be avoided. For example, to maximize shoreline bank erosion control, the wetland must not be located in an area where the fetch if > 1 mile due to the risk of failure in a newly constructed wetland. Also, information in the EPW models is useful because it provides design criteria with explicit measurements (e.g., percent basal cover >75%).
Contact person
F. Albert McCullough, Environmental Concern Inc., P.O. Box P, St. Michaels, MD 21663
phone: (410) 745-9620; fax: (410) 745-3517; e-mail: consult@wetland.org
Related procedures
EPW shares many concepts and terminology with the HGM Approach (Smith et al. 1995). EPW differs in the following ways:
Terminology, and
Models and variables are not scaled to a reference standard.
Extent of use/field testing
EPW has been used on large projects (e.g., reservoir and highways); watershed planning in Staten Island, NY; and smaller mitigation projects in Virginia, Maryland, Delaware, and New York. The full extent of use is unknown. Environmental Concern has applied EPW over 100 times in Staten Island and four times for other projects over the last two years.
Proposed future revisions
A draft floodflow alteration model has been prepared, but not published. There are plans to revise the shoreline bank erosion control model to include separate models for lake/coastal fringe and riverine areas.
Key Reference
Bartoldus, C.C., E.W. Garbisch, and M.L. Kraus. 1994. Evaluation for Planned Wetlands (EPW). Environmental Concern Inc., St. Michaels, MD. 327 pp. ppen.