A. OVERVIEW Chapter III: Wetlands and Their Functions
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lands such as cat‐tails, various sedges, speckled alder, These were completed on a county and red maple. The following summary describes each wide basis, and for Grafton County the of these three technical criteria: publication date was 1999. Mapping of Wetlands are classified according to their dominant Lebanon resulted in approximately Chapter III: Wetlands and Their Functions A. OVERVIEW Wetlands are lands that are transitional between up‐ lands and deep water habitats. They include swamps, marshes, bogs, and fens, as well as the fringes of lakes and ponds, rivers and streams. Along the coast they include estuaries, mudflats, tide pools, and the strand of the seashore itself. They are as old as the oceans and as new as rainwater pools in freshly excavated ground. They cover over 15% of the New England cover type, which is typically vegetated. The 1972 Fed‐ 1525 acres of hydric soils for the City. landscape; in Lebanon they cover at least 5.7% of the eral Water Pollution Control Act (renamed the Clean Hydric soil areas did not necessarily landscape exclusive of the two large lakes (Boston Lot Water Act when it was amended in 1977) established line up with NWI wetland areas, and and Mascoma) and the deepwater portions of the the National Wetlands Inventory (NWI) branch of the when these two map sources were Connecticut River. Both the state of New Hampshire U.S. Fish & Wildlife Service to classify and map all of compiled together the result was ap‐ and the Federal government use the following defini‐ the wetlands in the United States. In New England, proximately 1980 acres of wetlands in This initial wetlands map shows where tion for wetlands: 1 most of this work was completed in the mid 1980’s Lebanon (see map at right). the National Wetlands Inventory (NWI) and the Natural Resource Conservation “Wetlands are those areas that are saturated or inun‐ using black‐and‐white aerial photographs from the Wetland mapping was an important Service (NRCS) mapped wetlands. Com‐ dated by surface or ground water at a frequency and National High Altitude Aerial Photography Program. part of the NRI Project because of duration sufficient to support, and that under normal The mapping program followed the Classification of circumstances do support, a prevalence of vegetation their importance on the landscape. Wetlands and Deepwater Habitats of the United States typically adapted for life in saturated soil conditions. For millennia wetlands have served Wetlands generally include swamps, marshes, bogs, by Lewis Cowardin et al. (1979), and this system is still and similar areas” [42 Federal Register 37125‐26, 37128‐29, July 19, in use today. This initial mapping was fairly coarse, humankind by regulating floodwaters, 1977; NH RSA 482‐A:1] however, and on an average basis tends to under‐ recycling nutrients and sediment, pro‐ nificant step in the regulation of wetlands and water‐ The above definition identifies three technical criteria represent the number of wetlands in a given area by viding clean water to drink and wildlife to hunt. Mod‐ ways, and has governed their treatment since 1972. In for wetlands: water or hydrology, wet or hydric soils, as much as 50%. For example, in Lebanon, just 1039.2 ern day alterations to the landscape have elevated the New Hampshire the regulation of filling and dredging and vegetation that prefers wet soils, or hydrophytes. acres of wetlands were identified by the NWI program value of wetland function to unprecedented levels as of wetlands began three years earlier (1969), and the When and where all of these criteria are present on versus the 2000+ acres identified by this NRI Project. they have withstood damaging hurricanes and floods, state currently operates a joint permitting program the landscape comprise the very basis of a wetland. required billions on purifying the water, and faced Another “remote” method of mapping wetlands in the with the federal government. In spite of these safe‐ For example, water has to be present for a long wildlife extinction rates that are unparalleled in the region took place in the 1980’s and 1990’s by the Soil guards however, the state continues to lose wetlands enough period of time during the growing season for past 250 million years. The Clean Water Act was a sig‐ Conservation Service (now Natural Resource Conser‐ at an alarming rate – over 150 acres per year, which soil to develop certain characteristics that wetland 1 vation Service). The SCS used stereoscopic imagery of Both the NWI and SCS (NRCS) acreages of wetlands for Lebanon scientists define as hydric. Plants have to be predomi‐ include open water areas such as Boston Lot Lake, Mascoma Lake, although significant, is a mere fraction of the esti‐ the landscape to interpret the location of hydric soils. nantly hydrophytes, or those that typically live in wet‐ and the Connecticut River. mated loss of 361,000 acres per year in the Eastern Chapter III—Page 13 U.S.2 5. Educational Potential 6. Amount & type of previous disturbance series of mechanisms for conserving wetlands and of‐ in wetland fers recommendations for the protection of wetland Since 1980, a number of wetland evaluation systems 6. Scenic Quality function using both regulatory and non‐regulatory have been developed in the United States, including 7. Vegetation condition 7. Wetland‐based Recreation methods. federal government publications such as the Wetland 8. Organic matter accumulation 8. Floodwater Storage Evaluation Technique (WET I & II, USACOE Water‐ B. SAMPLING APPROACHES 9. Presence of invasive, weedy, or ruderal ways Experiment Station) and the Highway Methodol‐ 9. Groundwater Recharge/Discharge species Beginning in July 2008, wetlands in Lebanon were ogy Workbook and Supplement (USACOE), plus some 10. Sediment Trapping identified using a combination of map resources and state and regional systems such as Functional Assess‐ 10. Amount and condition of current hy‐ 11. Nutrient Trapping/Retention/ ment of Freshwater Wetlands: A Manual and Training drology Transformation Outline (Larson et al. 1989), and Method for the Com‐ 11. Hydrologic connectivity 12. Shoreline Anchoring parative Evaluation of Non‐Tidal Wetlands in New 12. Soil/substrate condition Hampshire (Ammann and Stone 1991). The latter For the assessment of wetlands in Lebanon, greater 13. Patch size relative to other wetlands in document is a recommended wetland evaluation emphasis was placed on Ecological Integrity than any a given area method for New Hampshire, although it is currently other function. Given the rapid current rate of devel‐ undergoing a significant revision and update and opment and the rate of loss of wetlands in the City, a The aerial view of Lebanon High School at right illustrates therefore was not used in Lebanon.3 focus on this function seemed appropriate since the an example of how wetlands can be fragmented and their ‘intactness’ of a wetland on the landscape natural buffers compromised. Besides a loss of wildlife habi‐ All wetlands have functions that tat and groundwater discharge/recharge, what other func‐ prescribes every other function it performs. tions are being impaired by the presence of impervious sur‐ serve the surrounding ecosys‐ State and regional methodologies typically faces such as parking lots and rooftops? tem. All of these functions con‐ begin with an assessment of ecological in‐ tribute to the well being of hu‐ Compare this with the well‐vegetated buffers behind Nature mans, therefore they are highly tegrity, but very few explore all of the essen‐ Walk as seen below. Which animal is helping control flood‐ valued by society tial biophysical attributes that comprise the ing? function. The only wetland assessment method that was found to contain a thorough evalua‐ Each of these methods addresses some of the salient tion of ecological integrity was Ecological Integrity functional values that wetlands contain, including but Assessment and Performance Measures for Wetland not limited to the following: Mitigation by NatureServe. In this method, ecological 1. Ecological Integrity integrity was measured on the basis of the following attributes: 2. Wetland Wildlife Habitat 1. Surrounding land use 3. Production Export 2. Landscape connectivity 4. Aquatic Life Support 3. Buffer length and width This chapter on wetlands and their functions reviews field observations. Initial wetland map information 2 Statewide wetlands loss data based on study by Vicki Chase et 4. Condition of buffer4 the methods used in mapping and delineating wet‐ was derived from NH GRANIT GIS data sources, in‐ al. (2006) as presented at the Annual Meeting of the NH Asso‐ lands, classifying them, and assessing their functions cluding the 1987 USGS data on surface water bodies, ciation of Wetlands Scientists, Concord, NH, 2006; data on the 5. Water quality rate of nationwide wetland loss provided by the USFWS Status and values. It describes the general condition of wet‐ the 1986‐7 NWI wetlands map for the region, and the 4 A “buffer” is an upland of variable width that lies immediately and Trends – Coastal Watersheds of the Eastern United States lands in Lebanon and highlights a few of the salient, 1999 Grafton County Soil Survey for hydric soils. The adjacent to a wetland. Buffers trap sediments, take up nutri‐ 1998 – 2004. ents, detoxify pollutants, and serve as wildlife habitat. high value wetland complexes. Finally, it provides a City of Lebanon Planning Office augmented these Chapter III—Page 14 map data with selected coverages that their GIS Coor‐ Wetlands Delineation Manual (ACOE Tech. Rpt. Y‐87‐ dinator had derived from a 2007 aerial photogram‐ 1). A Garmin 12XL GPS unit was used, with an average metric survey of the City, namely, a two‐foot contour precision of 3.2 to 7.7 meters. No attempt was made to interval data set, a culvert and ditches data set, and an correct these data or to conduct a legal survey of these intermittent and perennial stream data set.