At the Conservation Commission meeting of August 23, it was briefly discussed how some of the wetlands on Kohl Construction’s proposed condo site off North Street have been disturbed or filled. We came away concerned that some members of the commission did not take this issue seriously. One said something to the effect of, ‘Much of Boston is built on fill.’
Subsequent to the meeting, we became aware of Northampton’s Flood and Natural Hazard Mitigation Plan, approved by the City Council in 2004. This plan explicitly frowns on building on filled wetlands:
See also:
Northampton’s Flood and Natural Hazard Mitigation Plan: Floyd Flood Damage Reported Behind View Avenue; Avoid Building on Filled Wetlands
In a table of Existing Mitigation Strategies, the plan includes a “100 foot buffer around wetlands and the wetland resource area itself…” It says this strategy has been “Effective”, and says that an option to improve it would be to “Strengthen Wetland Ordinance”.
Benefits of Urban Wetlands and Their Buffer Areas
The loss of the water retention function of ephemeral ponds high in the watershed often necessitates downstream storm water control measures. It is much more effective to retain this upstream function than to try to restore wetland functions in downstream areas due to limited space and water volumes.
Subsequent to the meeting, we became aware of Northampton’s Flood and Natural Hazard Mitigation Plan, approved by the City Council in 2004. This plan explicitly frowns on building on filled wetlands:
Many areas of the City were developed before the passage of the Massachusetts Wetlands Protection Act of 1972. Historically filled wetlands are commonly related to problems with wet basements, flooding, shifting foundations and failed septic systems. Development in historically filled wetlands should be discouraged through zoning in order to protect health and safety… (p.24)In a similar vein, we are pleased to see that Chilmark’s wetland bylaws (Rich Text File) include filled and disturbed wetlands within the scope of its concerns. These bylaws also provide an excellent overview of the characteristics and benefits of wetlands. We have emphasized certain passages with bold type.
3.02 Vegetated Wetlands (Wet Meadows, Marshes, Swamps, and Bogs)
(1) Definition, Critical Characteristics and Boundary
(A) Vegetated Wetlands are freshwater wetlands, classified as wet meadows, marshes, swamps and bogs. They are usually areas where the topography is relatively flat, or areas of sheet flow on moderate slopes, and where the soils are perennially saturated. The ground and surface water regime and the vegetational community which occur in each type of freshwater wetland are specified in Section 3.02(1)(c) below. Freshwater wetlands also include: disturbed areas such as, but not limited to, filled or devegetated wetlands where the substrate is composed of hydric soils.
(B) The physical characteristics of Vegetated Wetlands, as described in the foregoing subsection (1)(a), are critical to the protection of the interests specified in Section 3.02(2) below.
(C) The boundary of Vegetated Wetlands is the line within which 50 percent of the vegetational community consists of the wetland plant species identified in Section 3.02(1)(c)(i) through (iv), below:
(i) The term “bogs” as used in this section shall mean areas where standing or slowly running water is near or at the surface during a normal growing season and where a vegetational community has a significant portion of the ground or water surface covered with sphagnum moss (Sphagnum sp.); disturbed areas such as, but not limited to, filled or devegetated areas where the substrate is composed of hydric soils and where the vegetational community is made up of a significant portion of one or more, but not limited to nor necessarily including all, of the following plants or groups of plants: aster (Aster nemoralis), azaleas (Rhododendron canadense and R. viscosum), black spruce (Picea mariana), bog cotton (Eriophorum), cranberry (Vaccinium macrocarpon), high bush blueberry (Vaccinium corymbosum), larch (Larix laricina), laurels (Kalmia augustifolia and K. polifolia), leatherleaf (Chamaedaphne calyculata), orchids (Arethusa, Calopogon, Pogonia), pitcher plants (Sarracenia purpurea), sedges (Cyperaceae), sundews (Droseraceae), sweet gale (Myrica gale), white cedar (Chamaecyparis thyoides), rushes (Juncaeae), and cinnamom fern (Osmunda cinnamonaea and O. regalis).
(ii) The term “swamps”, as used in this section, shall mean areas where ground water is at or near the surface of the ground for a significant part of the growing season or where runoff water from surface drainage frequently collects above the soil surface; disturbed areas such as, but not limited to, filled or devegetated areas where the substrate is composed of hydric soils and where a significant part of the vegetational community is made up of, but not limited to nor necessarily including all of the following plants or groups of plants: alders (Alnus), ashes (Fraxinus), azaleas (Rhododendron canadense and R. viscosum), black alder (Ilex verticillata), black spruce (Picea mariana), button bush (Cephalanthus occidentalis), American or white elm (Ulmus americana), white Hellebore (Veratrum viride), hemlock (Tsuga canadensis), highbush blueberry (Vaccinium corymbosum), larch (Larix laricina), cowslip (Caltha palustris), poison sumac (Toxicodendron vernix), red maple (Acer rubrum), skunk cabbage (Symplocarpus foetidus), sphagnum mosses (Sphagnum), spicebush (Lindera benzoin), black gum tupelo (Nyssa sylvatica), sweet pepper bush (Clethra alnifolia), white cedar (Chamaecyparis thyiodes), willow (Salicaceae), maleberry (Lyonia ligustrina), netted chain-fern (Woodwardia areolata) and Osmunda ferns.
(iii) The term “wet meadow”, as used in this section shall mean areas where ground water is at the surface for a significant part of the growing season and near the surface throughout the year and where a significant part of the vegetational community is composed of various grasses, sedges and rushes; disturbed areas such as, but not limited to, filled or devegetated areas where the substrate is composed of hydric soils; made up of, but not limited to nor necessarily including all, of the following plants or groups of plants: blue flag (Iris), vervain (Verbena), throughwort (Eupatorium), dock (Rumex), false loosestrife (Lythrum), marsh fern (Dryopteris thelypteris), rushes (Juncaceae), sedges (Cyperaceae), sensitive fern (Onoclea sensibilis), smartweed (Polygonum), horsetails (Equisetaceae), hydrophillic grasses (Gramineae)…
(2) Preamble
Vegetated Wetlands are areas where ground water discharges to the surface and where, under some circumstances, surface water discharges to the ground water.
Vegetated Wetlands are significant to wildlife and wildlife habitat, public or private water supply, ground water supply, flood control, storm damage prevention, prevention of pollution, the protection of fisheries, and the protection of shellfish.
The plant communities and soils of vegetated wetlands remove or detain sediments, nutrients (such as nitrogen and phosphorous), and toxic substances (such as heavy metal compounds) that occur in run-off and flood waters.
Some nutrients and toxic substances are detained for years in plant root systems or in the soils. Others are held by plants during the growing season and are released as the plants decay in the fall and winter. This latter phenomenon delays the impacts of nutrients and toxins until the cold weather period, when such impacts are likely to be lessened.
Wetlands help maintain water quality or improve degraded water by removing, transforming, and retaining nutrients; processing chemical and inorganic wastes and pollutants; and reducing sediment loads. Wetlands intercept runoff from uplands before it reaches the water and help filter sediments, nutrients, and wastes from flood water. It is important, however, to recognize that wetlands do not have an infinite capacity to perform this function.
Inland wetlands located along major streams and around lakes stabilize shorelines and channel banks and buffer developed uplands from storm, wave, or erosion damage. During dry periods the water retained in vegetated wetlands is essential to the maintenance of base flow levels in streams and recharge into the groundwater.
Undisturbed natural wetland communities have high value as prime examples of their community type, as areas of study and comparison, and for protection as a unique resource. The existence of a buffer area of undisturbed natural vegetation adjacent to a wetland is important because many wetlands species spend the majority of their non-breeding and non-feeding lives in the areas immediately adjacent to a wetland.
The profusion of vegetation and the relatively flat topography of vegetated wetlands slows down and reduces the passage of flood waters during periods of peak flows by providing temporary flood water storage, and by facilitating water removal through evaporation and transpiration. This reduces downstream flood crests and resulting damage to private and public property. During dry periods the water retained in vegetated wetlands is essential to the maintenance of base flow levels on rivers and streams, which in turn is important to the protection of water quality and water supplies.
Wetland vegetation provides shade that moderates water temperatures critical to fish life. Wetlands flooded by adjacent water bodies and waterways provide food, breeding habitat and cover for fish. Fish populations in the larval stage are particularly dependent upon food provided by overbank flooding which occurs during peak flow periods (extreme storms), because most river and stream channels do not provide quantities of the microscopic plant and animal life required.
Wetland vegetation supports a wide variety of insects, reptiles, amphibians, mammals, and birds which are a source of food for important game fish. These wetlands are also important to the protection of rare and endangered wildlife, flora and fauna species. Vegetated wetlands serve
to moderate and alleviate thermal shock and pollution resulting from run-off from impervious surfaces which may be detrimental to wildlife, fisheries, and shellfish downstream of the vegetated wetland.
The maintenance of base flows by vegetated wetlands is likely to be significant to the maintenance of a proper salinity ratio in estuarine areas downstream of the vegetated wetland. A proper salinity ratio, in turn, is essential to the ability of shellfish to spawn successfully, and to therefore provide for the continuation of shellfisheries.
Vegetated Wetlands support sport fishing, hunting, birdwatching, nature observation and study, and other wetland-related uses which in turn generate capital for a local economy and pure enjoyment for those participating in these forms of recreation.
Land within 100 feet of a Vegetated Wetland is likely to be significant to the protection and maintenance of vegetated wetlands, and therefore to the protection of the interests which these resource areas serve to protect.
3.04 Land Subject to Flooding (both Bordering and Isolated Areas, and Vernal Pools)
…Isolated Land Subject to Flooding and Vernal Pools are isolated depressions or closed basins which serve as a ponding area for runoff or high ground water which has risen above the ground surface. Such areas are likely to be locally significant to flood control and storm damage prevention. In addition, where such areas are underlain by pervious material they are likely to be significant to public or private water supply and to ground water supply. Where such areas are underlain by pervious material covered by a mat of organic peat and muck, they are also likely to be significant to the prevention of pollution. Isolated Land Subject to Flooding provides a temporary storage area where runoff and high ground water pond and slowly evaporate or percolate into the substrate. Filling causes lateral displacement of the ponded water onto contiguous properties, which may in turn result in damage to said properties. Isolated land subject to flooding and Vernal Pools provide important breeding habitat for amphibians and some rare plants. Vernal Pools hold water for at least two continuous months, but contain no fish predators.
Isolated Land Subject to Flooding, where it is underlain by pervious material, provides a point of exchange between ground and surface waters.
Contaminants introduced into said area, such as septic system discharges and road salts, find easy access into the ground water and neighboring wells.
See also:
Northampton’s Flood and Natural Hazard Mitigation Plan: Floyd Flood Damage Reported Behind View Avenue; Avoid Building on Filled Wetlands
In a table of Existing Mitigation Strategies, the plan includes a “100 foot buffer around wetlands and the wetland resource area itself…” It says this strategy has been “Effective”, and says that an option to improve it would be to “Strengthen Wetland Ordinance”.
Benefits of Urban Wetlands and Their Buffer Areas
The loss of the water retention function of ephemeral ponds high in the watershed often necessitates downstream storm water control measures. It is much more effective to retain this upstream function than to try to restore wetland functions in downstream areas due to limited space and water volumes.