Maintaining Wetlands & Floodplains


Legally the term "wetland" includes not only areas we typically think of as wetland, such as salt and cattail marshes, but also intermittent streams and other areas that may appear dry for a portion of the year. Activities in or near "bordering vegetated wetlands (BVWs) - marshes, swamps, and bogs adjacent to water bodies and coastal beaches are regulated. Floodplains, banks, dunes, beaches, tidal flats, banks of and land under rivers, streams, lakes, and ponds; and a 200 foot wide riverfront area on both sides of perennial rivers are also protected. Technical definitions are found in the law and its accompanying regulations (310 CMR 10) as well as the Cohasset Wetlands Bylaw and Regulations.

The Conservation Commission usually has jurisdiction 100 feet from the edge of a resource area. The first 50 feet from the resource area is the inner buffer zone or the "no touch" zone, and the remaining 50 feet is the outer buffer zone. The exceptions are vernal pools, isolated land subject to flooding, and isolated vegetated wetlands. These have a 25 foot buffer zone as defined in the Cohasset Wetlands Bylaw and Regulations. The 100 year floodplain does not have a buffer zone.

Vernal Pools

Are defined as any ponding area that holds water for two consecutive months between December and June and meets state certification criteria.


A floodplain of any water body, inland or coastal is simply defined as the landward extent of flooding following a statistical 100 year frequency storm. Floodplains are typically identified as Zone A (or sometimes V in coastal areas) on flood insurance rate maps prepared by the federal Emergency Management Agency (FEMA). Both Bordering and Isolated Lands Subject to Flooding are regulated.

Isolated Land Subject to Flooding

These areas are defined by the Cohasset Wetlands Regulations as any ponding area within a depression that provides temporary storage area of standing water with no minimum size criteria.