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 New Hampshire.
Categories assessed
Fourteen functional values are addressed: ecological integrity; wetland wildlife habitat; finfish habitat; educational potential; visual/aesthetic quality; water based recreation; flood control potential; ground water use potential; sediment trapping; nutrient attenuation; shoreline anchoring and dissipation of erosive forces; urban quality of life; historical site potential; 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).
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
Total 13-29 hours.
8-24 hours: Determine study area (step 1), assemble available information (step 2), prepare wetland base map and overlays (step 3), and determine watershed boundary (step 4).
4 hours per wetland: Collect field data (step 5)
1 hour per wetland: Complete data sheets (step 6), fill out summary sheets (step 7), rank wetland for each functional value (step 8), and give highest ranking wetlands in each functional value a "1" for noteworthiness (step 9).
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 New Hampshire.
Comparison of habitat types
Can directly compare nontidal wetlands in New Hampshire.
Use as guide to design
The NH Method 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 limits its application for this purpose. For example, the NH 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). In some circum stances, 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 wetland that is not a bog - Part B,#3). 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
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
Related procedures
There are several related procedures. The NH Method is based upon the CT Method (Ammann et al. 1986), but modified and adapted New Hampshire inland wetlands. The Coastal Method (Cook et al. 1993) is a version 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 NH Method has been used for townwide landuse planning and not for impact assessment. It has been used at least twenty times over the last two years.
Proposed future revisions
None planned.
Key Reference
Ammann, A.P. and A. Lindley Stone. 1991. Method for the Comparative Evaluation of Nontidal Wetlands in New Hampshire. NHDES-WRD-1991-3. New Hampshire Department of Environmental Services, Concord, NH.