Primary purpose
To evaluate wetlands in planning, education, and wetland inventory; but not for detailed impact analysis on individual wetlands.
Expertise needed
Public officials and others who have some familiarity with wetlands, but who are not necessarily wetland specialists.
Applicable habitat types
Nontidal wetlands in Connecticut.
Categories assessed
Thirteen functional values are addressed: flood control; ecological integrity; wildlife habitat; finfish habitat for watercourses associated with wetland; nutrient retention and sediment trapping; educational potential; visual/esthetic quality; agricultural potential; water-based recreation in watercourse associated with wetlands; groundwater use potential; shoreline anchoring and dissipation of erosive forces; and noteworthiness.
Procedure
The user(s) assembles available information (e.g., soil survey, topo maps, zoning maps), prepares a wetland base map and overlays, visits a wetland area, and completes data sheets that (a) contain evaluation questions, (b) list evaluation criteria for each question, (c) assign a functional value index (FVI) (scale 0-1.0) to criteria for each question, and (d) includes a space for calculating the average functional capacity index. Wetland value units (WVUs) are also calculated for each functional value and the results are then analyzed.
Key Terminology
Average FVI: an index indicating the relative functional value of all wetlands in an area (e.g., a town). Average FVI is calculated by averaging functional value indices (1.0 = optimal functional value; 0 = no functional value).
Functional value: practical measurable values of a wetland.
Functional value index (FVI): index assigned to each evaluation criteria (scale 0 - 1.0).
Rating: rating assigned to each evaluation criteria for the flood control functional value (scale 0 - 9).
Wetland value units (WVUs): measure of functional value incorporating size of the wetland area (WVU = Average FVI x size of wetland assessment area).
Estimated time to assess 1 acre site
8-24 hours: Determine study area (step 1), assemble required information (step 2), and prepare
wetland map and overlays (step 3).
4 hours per wetland: Collect field data (step 4)
1 hour per wetland: Finish data sheets in office (step 5), fill out summary sheets for each wetland
(step 6), rank wetlands for each functional value (step 7), and give highest ranking wetlands in each functional value a "1" for noteworthiness (step 8).
Output
Measure of functional value of a site; to be used for noting relative value of all wetlands within a town or selected watersheds in Connecticut.
Comparison of habitat types
Can directly compare nontidal wetlands within Connecticut.
Use AS guide to design
The CT Method models should not be used as a guide to design; however, individual variables (evaluation questions) 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 CT Method uses opportunity variables, but does not set upper limits on those opportunities that could potentially reduce functional value (e.g., excess nutrient input from the watershed is assigned a high index for the nutrient attenuation functional value).
Contact person
Alan Ammann, Natural Resources Conservation Service, Federal Building, 2 Madbury Road, Durham, NH 03824-1499
phone: (603) 868-7581; fax: (603) 868-5301; e-mail: apa@nh.nrcs.usda.gov
In some circumstances, a wetland may not have the capacity to remove all nutrient input (it’s functional value may be substantially reduced). 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 NH Method does not provide validated threshold values for many variables. Some of the variables may provide useful information. Users can refer to the variables to determine which conditions increase or decrease functional value. This can be translated into design criteria with explicit measurements (e.g., design a forested or scrub-shrub wetland- Part B,#2). Finally, the design criteria for some variables may be unsuitable and the overall rating of function may be misleading for the reasons given above.
Related procedures
There are several related procedures. Two are based upon the CT Method, but are modified and adapted to New Hampshire. The NH Method (Ammann and Lindley Stone 1991) is adapted to New Hampshire inland wetlands and the Coastal Method (Cook et al. 1993) is adapted to New Hampshire coastal wetlands. Portions of the CT Method are incorporated into the VIMS Method (Bradshaw 1991). OFWAM (Roth et al. 1996) used the NH Method as a template; however, there are substantial differences. In addition to adapting the models to Oregon, several functions have been removed or combined and the scoring/output has been changed.
Extent of use/field testing
The CT Method has been used primarily for land use planning. The extent of use is unknown.
Proposed future revisions
None.
Key Reference
Ammann, A.P., R.W. Frazen, and J.L. Johnson. 1986. Method for the Evaluation of Inland Wetlands in Connecticut. DEP Bulletin No. 9. Connecticut Department of Environmental Protection, Hartford, CT.