On
June 20 , 2005, Mark West, of West Environmental Inc., presented the
results of a 2 year inventory and field study of Manchester' s
wetlands to the public and city officials. The presentation was
presented in Manchester's aldermanic chambers and was taped by MCTV
(Channel 22.) The study, which had been performed for the Manchester
Conservation Commission, was also provided in written form to the
MCC. The written version noted that "The need for extra protection
for wetlands in southern New Hampshire has been clearly shown by
rapid development and wetlands degradation that has occurred over the
past 15 years."
The wetlands study was undertaken with the hope that Manchester will eventually designate some of its higher-quality wetlands as "prime wetlands." In this case the wetlands would receive "extra protection" from development. The NH Code of Administration Rules ("Rules") Wt.70l.02 provides criteria for the selection of wetlands that would receive this designation. These wetlands must have hydric soils (at least 50% hydric A and the remaining hydric B), hydrophytic vegetation and wetland hydrology. West Inc.therefore sought to obtain background data on the location, and soil type and drainage of Manchester's wetlands. Size of the wetlands was also an important consideration.
The size of the wetlands was made from the 1990 Natural Wetlands Inventory Map (NWIM) as well as a City of Manchester watershed boundaries map. The soil type and drainage class of these wetlands was determined from the Hillsborough County Soil Survey Map. USGS topographic maps and a City of Manchester watershed boundaries map were used to determine wetland topography and association of streams or rivers.
The designation of prime wetlands also calls for the selection of evaluative criteria. West therefore prepared a field evaluation form based on 7 "functions" and 3 "values" selected from a list that appears in the Code of Administration "Rules". 1 additional "value" was added by West.
The functions selected were: 1. Groundwater Recharge/Discharge; 2. Floodflow Alteration ; 3. Sediment/Toxicant/Pathogen Retention; 4. Nutrient Removal/Transformation; 5. Production Export; 6. Sediment Shoreline Stabilization and 7.Wildlife Habitat
The values selected were: 1. Recreation; 2. Education/Scientific; and 3. Uniqueness/Heritage. A fourth value (Mitiation Potential) was added.
The West study involved ground field observations of each wetlands. A field study guide was prepared and the wetlands were systematically evaluated, and the data collected from each one was recorded. (Many of the studies were performed by Bobby Jean Weiler and Kym Hall.) In the field studies, the boundaries for each wetland were confirmed, as well as hydrologic connections and the presence of hydric soils A and B. Vegetation type and its density and diversity were also observed, as well as signs of wildlife. The field evaluation form also required a determination as to whether or not a given wetland fulfilled each of the eleven functions and values. For each wetlands examined, a "yes" or "no" was circled for each criterion. The field observations were also correlated with aerial photographs of the wetlands areas.
II.
WETLANDS FUNCTIONS AND VALUES
The definitions of the functions and values are as follows:
1. Groundwater Recharge/Discharge
This function involved the potential for the wetland to contribute water to an aquifer or the potential for the wetland to serve as an area where ground water can be dischared to the surface.
2. Floodflow Alteration
This function is the effectiveness of the wetland on reducing flood damage and attenuation of floodwater for prolonged periond following precipitation events.
3. Sediment/toxicant/pathogen Retention.
This function reduces or prevents degradation of water quality. It relates to the effectiveness of the wetland as a trap for sediment, toxicants, or pathogens.
4. Nutrient Removal/Retention
This function relates to the effectiveness of the wetlands to prevent or reverse the effects of excess nutrients entering aquifers or surface water such as ponds, lakes, streams, rivers or estuaries. The removal or transformation process is in the vegetated buffer and water column.
5. Production Export
This function relates to the effectiveness of the wetland to produce food or usable products for humans or other living organisms.
6. Riverline Shoreline Stabilization
This function is the effectiveness of a wetland to stabilize stream banks and shorelines against erosion.
7. Wildlife Habitat
This function considers the effectiveness of the wetland to provide habitat for various types and populations of animals typically associated with wetlands and wetlands edges. Both the resident and migrating species are considered in this function. It also considers endangered species habit and the presence of endangered or rare species that have been identified by the New Hampshire Natural Heritage Inventory (NHNHI.)
1. Recreation
This value considers the effectiveness of the wetland and associated water courses to provide recreational opportunities such as canoeing, boating, fishing, hunting, birding, walking and other passive recreational activities.
2. Educational/Scientific
This value considered the effectiveness of the wetland as a site seen as an "outdoor classroom" or as a location for scientific study or research.
3. Uniqueness/Heritage
This value relates to the effectiveness of the wetland or its associated water body to produce certain special values such as historical events, unique or rare plants, animals or geological features, archeological sites, and unusual aesthetic quality.
4. Restoration Potential (Mitigation)alking and other active and passive recreational activites
This is a value that was added by West. He suggested that a "library" of wetlands fulfilling this value by kept, and made available to developers, so that restoration of some of these wetlands might be considered by them as mitigation possibilities.
At a more recent
meeting of the Manchester Conservation Commission (January 5, 2006),
Mark West and Kym Hall reviewed the Manchester wetlands that should
be most appropriate for designation as prime wetlands. The following
table gives the Wetland ID # (the wetlands have not yet been named.),
the size in acres, and some field notes about each of these
wetlands.
WETLAND ID # SIZE IN ACRES NOTES Wetland 4 300 Part of Cohas Brook system - Largest and most diverse system in the City. - Invasive species - phragmites, bittersweet - Degradation by pipeline.
Wetland 17a 13 Buffer to Massabesic Lake - Public drinking waer supply - Poor level fen/bog system
Wetland 17b 16 Buffer to Massabesic Lake - Public drinking water supply - Good forested buffer.
Wetland 19 23 Headwaters of Hogg Brook - Degradation by pipeline:some fill - Good forested buffer to east and some to west.
Wetland 20 15 NHI rare bird and reptile habitat - Degradation by pipeline, fill, runoff (residential)
Wetland 25a 22 American bittern; spotted turtle - Poor level fen/bog system
Wetland 25b 6.5 American bittern; spotted turtle - Poor level fen/bog system
Wetland 25c 10 American bittern; spotted turtle - Poor level fen/bog system
Wetland 30 19 Hackett Hill Wetlands - Associated with Millstone Brook - Invasives-loosestrife; Degradation-powerline - Good forested buffer - Waterfowl habitat; wildlife habitat/corridor
Wetland 31 26 Hackett Hill Wetlands - Wildlife habitat corridor: blue heron rookery, otters present, waterfowl habitat; - Degradation by extensive development in progress along entire eastern and southern bounds - All three inlets/outlets recently culverted/crossed
Wetland 32 12 Hackett Hill Wetlands - Atlantic white cedar/giant rhododendron swamp; globally rare - only one north of CT
Wetland 33 23 Hackett Hill Wetlands - Good forested buffer - Black gum trees - Wildlife habitat/corridor - Atlantic white cedar/black gum/giant rhododendrons
Wetland 35 22 Hackett Hill Wetlands - Wildlife habitat/corridor - Good forested buffer -Atlantic white cedar/black gum/black spruce/giant rhododendrons
Wetland 50: Wetland 51 19 and 3 Great blue heron rookery - Wildlife habitat/corridor - Good forested buffer - Atlantic white cedar
Wetland 52a 3 Black gum swamp - Wildlife habitat-corirdor - Good forested buffer
Wetland 52b 0.3 Black gum swamp - Wildlife habitat-corridor - Good forested buffer
Wetland 54 0.6 Atlantic white cedar - Wildlife habitat/corridor - Good forested buffer
Wetland 55 0.5 Atlantic whtie cedar - Wildlife habitat/corridor - Good forested buffer
It can be noted that eleven of the selected wetlands are in the Hackett Hill area. Many of them are located within the boundaries of The Nature Conservancy's Manchester Cedar Swamps Preserve. A map will shortly be provided on this Web page so that the precise locations of the wetlands can be noted. Progress on the "prime wetlands"designation undertaking will also be reported here.
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