Amherst Wetland Assessment
And
Prime Wetland Designation Project
Amherst, NH

APPENDIX D
FUNCTIONAL VALUE SPECIFICATIONS
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FVI 1 – Ecological Integrity

  1. Estimation of the amount of hydric a soil was always field checked
  2. Dominant land use zoning was identified as agriculture, forestry or similar open space zoning
  3. Water quality was estimated based on surrounding land use; i.e. it was not field tested
  4. The density of buildings within the 500 ft buffer was also field checked
  5. The amount of fill was always estimated visually, and included only the amount of non-hydric fill
  6. Woodland and idle land included all undeveloped, non-agricultural land
  7. Level of human activity in the wetland was estimated after the entire wetland edge was walked
  8. Level of human activity within the 500 ft buffer was visually estimated after the edge was walked
  9. Plant community impacts included logging; invasive species effects were estimated on winter presence
  10. Percent of wetland being drained was visually estimated during the high water table time period (N/A in this study)
  11. Number of public road crossings included those that ran along the edge of the wetland; however these were only counted once even if they extended beyond 500 feet in length along the edge of the wetland
  12. Artificial dams that altered the flow of water yet supported sufficient flow through a culvert were assigned a .5 value; beaver dams that were inactive or broken yielded a 1.0 value; beaver dams that were active but which did not significantly alter the wetland size were assigned a .75 value

FVI 2 – Wetland Wildlife Habitat

  1. FVI1 index derived from above
  2. Area of shallow permanent water was always estimated in field based on winter condition
  3. Water quality was estimated based on surrounding land use; i.e. it was not field tested
  4. Wetland classes were determined to be present only if in discernible amounts – i.e. >5% of the total wetland area or .25 acres, whichever was larger
  5. Dominant wetland class was determined areally; intergrades (e.g. PEM/SS) were allowed based on height
  6. Minimum interspersion size was approximately .25 acres; at least 3 patches each of at least 2 wetland classes had to have been present
  7. Wetland juxtaposition was based on perennial stream or other open water connectivity as determined in field; adjacency to other unconnected wetlands was based on NWI map
  8. Island minimum size: .1 acres; did not have to be separated by open water
  9. Wildlife access was present if at least one strip >50 feet wide existed to another wetland; however, the other wetland could have been hydrologically connected
  10. Percent of wetland edge bordered by upland wildlife habitat was applicable to all non-developed lands (incl. agricultural)

FVI 3 – Finfish Habitat – Streams & Rivers

(Zero entered for all fields unless perennial stream was visibly present at time of assessment)

PART A – stream name (if any) based on USGS map; size in acres based on average width times length

  1. Dominant land use in watershed was based on USGS map AND field survey as necessary; intergrade land uses allowed – e.g. .75 or .25 values OK
  2. Water quality was estimated based on surrounding land use; i.e. it was not field tested
  3. Barriers to anadromous fish N/A – all streams in Northwood beyond range; therefore 1.0 value assigned
  4. Stream bank width was estimated as average width from beginning of wetland boundary to end
  5. Available shade was visually estimated in field as described in method
  6. Stream modification applicable mostly to culverts and channels between hydrologically connected wetland units
  7. Abundance of cover objects – included estimated presence of floating aquatic vegetation
  8. Spawning areas were visually estimated based on all species of fish (i.e. not just stocked or anadromous)

PART B – size of pond or lake estimated in field, or if large, estimated using a dot grid and map (also checked against NWI map information)

  1. Dominant land use as above
  2. Water quality as above
  3. Barriers to anadromous fish as above
  4. Total area estimated as above
  5. Abundance of cover objects was estimated visually as above
  6. Percent of rooted vegetation was based on visual estimate of summer condition

FVI 4 – Educational Potential

(Site located at easiest access point(s) and comprised area accessible within a 15 minute walk)

  1. Ecological Integrity FVI from above
  2. Wetland Wildlife Habitat FVI from above
  3. Proximity to schools based upon ability to walk to wetland, or of school bus to drive to wetland (i.e. not for 4WD drive vehicles)
  4. Presence of nature preserve or other wildlife management areas based upon Special Features map of Northwood; included tree farms, conservation & deed restricted properties; 1.0 assigned only for publicly owned wildlife or nature preserve areas; .75 for tree farms; .50 for all other protected areas
  5. Proximity to other plant communities always present; only condition otherwise would have been active farmland that immediately bordered the wetland on all sides
  6. Off-road parking present (suitable for school buses) only if within 15 minutes walk of wetland; moderate expense assumed to develop parking area unless wetland difficult to get to and more than a fifteen minute walk from the nearest access point
  7. Number of wetland classes was tallied for area within 15 minute walk of primary access point
  8. Access to perennial stream present only if stream within 15 minute walking radius of primary access point
  9. Access to pond or lake same as above
  10. Student safety assessment based on attributes listed; bush-wacking not applicable; no .10 values assigned
  11. Public access prohibited if most or all of wetland posted or fenced off; otherwise, some public access assumed; unlimited access applicable only to wetlands along busy roads
  12. Visual/aesthetic detractors primarily road noise; intergrades allowed
  13. Handicap accessibility present only if paved or gravel road surface present adjacent to wetland edge

FVI 5 – Visual/Aesthetic Quality

(Viewing sites located at principal access points, or if several available, from the locale(s) that presented the greatest opportunity to view the entire wetland)

  1. Number of wetland classes based on minimum size of .25 acres per wetland class
  2. Dominant wetland class based on attributes listed; intergrades acceptable if clearly a mixture of visible classes
  3. Noise principally from roads, based on winter condition of surrounding vegetation
  4. Odors present based on winter condition; unnatural odors primarily due to vehicle exhaust
  5. Visible open water extent based on visual estimate at time of assessment, not summer condition
  6. General appearance based on winter condition; minor detractors primarily skid trails, litter, etc.; severe detractors principally the developed landscape
  7. Landform contrast subjectively determined; mostly moderate to low; intergrades often given
  8. Dominant surrounding land use mostly 1.0, unless extensive residential and/or commercial areas present
  9. Area of flowering trees & shrubs, or those that turn vibrant colors in fall based on observed presence and amount of deciduous vegetation
  10. Wetland Wildlife Habitat as above

FVI 6 – Water-based Recreation in Watercourse Associated with Wetland

(Only evaluated for wetlands with permanent open water that would support non-powered boats)

  1. Fishing – data on stocked streams came from local sources; when in doubt, occasional use was assumed, unless stream or pond was too shallow to support game fish
  2. Hunting – posted signs seen in the field were the only reason to assume hunting prohibition
  3. Wildlife as above
  4. Water quality as above
  5. Canoe and boat passage assumed as defined, even though some wetlands had very small areas for passage
  6. Off-road parking value assumed 4WD access as well; 15 minute walking limit used as in FVI4 and FVI5
  7. Access also assumed 4WD road usage; moderate expense typically assigned
  8. Visual/aesthetic quality from above

FVI 7 – Flood Control Potential

(Wetland and watershed acreage derived from sources described above; Wetland Control Length (WCL) based on field observation; 0.0 assigned for two wetlands that were effective basins without an inflow or outlet)

  1. Total wetland acreage as above
  2. Total watershed size as above; some discrepancy with GIS data for watersheds that lay mostly outside of the Town boundaries (used dot grid and topo for these)
  3. WCL measured in field at one foot flood stage at the outflow point; for stream outflows, WCL point chosen at narrowest width of stream channel immediately below the end of the palustrine wetland
  4. Calculations completed in field, and checked using Microsoft Excel spreadsheet
  5. FV index selected from table as given; whole tenths of an integer used; some intergrade points assigned where scale equivalencies warranted a clear selection – i.e. if Ratio A was 5 and Ratio B was 3, an FVI of .9 was assigned

(Sketches of the WCL was completed on field sheets for the 32 wetlands I was assigned)

FVI 8 – Ground Water Use Potential

(All wetlands were evaluated for this function, even if the wetland was greater than 1 mile from a stratified drift aquifer; presence of the latter was based upon NH GRANIT aquifer maps for Northwood and surrounding towns)

  1. The presence of public wells was determined from the ground water hazard overlay map; private wells were assumed to be present at all occupied residences observed within 1 mile downstream of the wetland
  2. Stratified drift aquifers were determined from the water resources map of the Northwood CC
  3. Ground water quality was always assumed to meet NH DES drinking water quality standards
  4. Water quality of watercourse as above

FVI 9 – Sediment Trapping

PART A - Opportunity

  1. Average slope of the watershed was calculated as described in the NH method; at least 6 transverse lines both north-south and east-west were used for larger (e.g. > 25 acre) wetlands; 4 transverse lines were used for smaller wetlands
  2. Potential sources of excess sediments were visually estimated based on observed and assumed land use in watershed

PART B – Overall Potential

  1. Opportunity from Part A
  2. Flood water storage from FVI 7
  3. Average observed wetland border was used in this attribute
  4. Dominant wetland class border was determined in the field as the class with the greatest amount of areal coverage; scrub shrub and dense cattails were assigned 1.0, forested wetland borders were assigned .5, all others were assigned 0.1 including those where no open water body was present; intergrade index points were acceptable
  5. Areas of impounded water included all non-flowing open water bodies

FVI 10 – Nutrient Attenuation

PART A – Opportunity

  1. Opportunity for sediment trapping from above
  2. Potential sources of excess nutrients based on field and assumed conditions in the watershed; 1.0 assigned for areas with septic systems immediately adjacent to the wetland; intergrades occasionally assigned

PART B – Overall Potential

  1. Opportunity for nutrient attenuation from above
  2. Overall potential for sediment trapping from above
  3. Dominant wetland class determined in field as described; only 2 "bogs" found
  4. Area of water impoundment determined in the field as in FV 5 above

FVI 11 – Shoreline Anchoring and Dissipation of Erosive Forces

(Zeroes were assigned for this function for all wetlands without permanent open water)

  1. Wetland morphology determined in the field, based on assumed growing season condition; all distinct shorelines assessed and computed for evaluation area
  2. Width of wetland border estimated for growing season condition
  3. Vegetation density estimated in field from assumed summer condition

FVI 12 – Urban Quality of Life

(Not assessed for the Town of Amherst)

FVI 13 – Historical Site Potential

(This function was only assessed for those wetlands where historical sites were observed, as determined in the field through direct observation of historic structures; stone walls did not count as ‘significant’; the area of the potential historical site was estimated based on the size and extent of the visible structures, and was never less than 1 acre; the average FVI was assigned a 1.0 if the site was well known locally for its historical significance)

  1. Proximity of potential site to a perennial stream was visually estimated
  2. Visible structures had to be quite evident in order to be recorded
  3. Existence of mill pond had to be determined through local knowledge, unless the dam and outflow or mill race was still intact
  4. Historical buildings had to be recognized as being locally significant and associated with the wetland and water course

FVI 14 – Noteworthiness

  1. Determination of the presence of rare and endangered species was made through written communication with the NH Natural Heritage Program
  2. Local knowledge (i.e. the Amherst CC) was utilized for determining whether the wetland was used for scientific research
  3. The NH Natural Heritage Program also provided information on rare or exemplary natural communities; for example, the presence of several black gum swamps in Northwood suggested that others needed to be looked for
  4. Local significance based upon high WVU scores was assessed upon completion of the data analysis; all wetlands with top (1st, 2nd, or 3rd) WVU scores were assigned a 1.0 for this question
  5. Local significance for other reasons was determined on the basis of the presence of other unique attributes that were not recognized by the above attributes; the most common example of this was the presence of great blue heron nests which could not be confirmed as being active in the breeding season
  6. Important archaeological information was supplied by the Amherst CC; no sites were known to be present in the Town
  7. Hydrologic connection to a federally designated river was determined for all wetlands in the Lamprey River watershed