Amherst Wetland Assessment
And
Prime Wetland Designation Project
Amherst, NH
EXECUTIVE SUMMARY
January 2000
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Amherst Wetland Assessment And Prime Wetland Designation Project Amherst, NH EXECUTIVE SUMMARY January 2000 |
In the summer and fall of 1999, fieldwork was completed on a town-wide project to assess the prime wetlands in the Town of Amherst, New Hampshire. The work officially began in March of 1999 upon notification of receipt of a Local Initiatives Grant of the NH Department of Environmental Services Water Protection Program. At that time, the Town of Amherst secured matching funds from both the Amherst Conservation Commission and the Pennichuck Water Works Corporation in order to expedite the completion of the study. Contracted work by Antioch New England Graduate School began by the author and three Antioch students in late March and was completed by the end of January 2000. Field work on 100 wetlands was completed between June 27 and October 25, 1999 using the "Comparative Evaluation of Non-tidal Wetlands In New Hampshire" (1991). Preliminary analysis was accomplished by early November 1999, at which time a presentation was made to the Town of Amherst as a part of a preliminary review of those wetlands that were evaluated. Suggestions for prime wetland criteria were made, and a point system suggested that emphasized ground and surface water protection, especially in the Pennichuck watershed. This report contains the results of the town-wide wetlands evaluation, as well as suggested ordinance language that recognizes and protects those wetlands that are identified as potential candidates for prime wetland designation.
The 100 wetlands that were evaluated comprise a total of 2242.7 acres, or 10.1% of the total land and water area of Amherst (22,272 acres). The amount of wetland area assessed represents roughly 90% of the wetland area in the Town according to the 1986 National Wetland Inventory map. The remaining wetland acreage, which was excluded from the inventory, was largely comprised of small, isolated wetlands. The size of the 100 wetlands that were assessed ranged between 1.0 and 230 acres, with a mean size of 23.27 acres. Wetland Value Units (WVU’s) ranged between .10 and 230.0, with a mean of 9.38, whereas Functional Value Indices (FVI’s) ranged between .10 and 1.0, with a mean of .45. Fifteen wetlands held the top three WVU rankings among all of the functions that were assessed. One additional wetland held the highest three ranks for individual Functional Value Indices. Two others contained rare or endangered species even though their WVU or FVI ranks were not among the highest scores.
Wetlands were initially ranked according to their WVU’s and FVI’s. Feedback from Town officials suggested extra weighting for the purpose of water quality protection, specifically, for those wetlands in the Pennichuck watershed, those above or immediately upstream of an aquifer, and those within .5 mile of a public water supply well. The above WVU and FVI cumulative point rank (CPR) was modified using a constant based on these three criteria, or CPR*1/(1+k), where k = the numerical count of the presence of these criteria (N = 1, 2 or 3). The resultant calculation provided a distinct list of 44 wetlands that were subsequently recommended for prime wetland designation.
The following report contains a description of the methods used in the assessment and analysis process, as well as a detailed account of the wetland ordinance revision process. Charts, graphs, and maps of candidate prime wetlands can be found in the Appendix.