The Massachusetts Wetlands Protection Act (MGL Ch. 131 s.40) and its regulations (319 CMR 10) issued by the Massachusetts Division of Environmental Protection establish the science-based legal definitions used to identify and delineate wetlands and floodplains. Rivers, streams, lakes, and ponds are easy to identify and are generally found on town maps. Perennial streams shown on the U.S Geologic Survey topographic maps are presumed to have protected riverfront areas. However, a stream’s status as perennial or intermittent can be overcome with sufficient technical evidence. Vegetated wetlands are identified on the basis of their hydrologic characteristics (i.e. how wet they are). Characteristic vegetation - such as skunk cabbage, cinnamon fern, tussock sedge, high bush blueberry, is used to identify the presence and location of swamps, marshes, wet meadows, and other types of vegetated wetlands. Soil characteristics that reflect saturated soil conditions at or near the ground surface are also used. The top of bank is found at the first break in slope or the mean high water level. Bordering Land Subject to Flooding is identified by the Federal Emergency Management Agency for flood insurance purposes, by engineering calculations, or with reliable historical observations.
The Carlisle Conservation Commission has maps that show the approximate location of wetland boundaries throughout the town. However, such maps can only be used as guidance. Actual field delineations are required of permit applicants. The assistance of a wetland consultant and a land surveyor is often required to identify and delineate wetlands and floodplains. The Conservation Commission office can provide a list of consultants who have worked in Carlisle although the commission does not recommend specific firms or individuals.