Wetlands vary widely because of regional and local differences in soils, topography, climate, hydrology, water chemistry, vegetation, and other factors, including human disturbance. Indeed, wetlands are found from the tundra to the tropics and on every continent except Antarctica. Wetlands generally include swamps, marshes, bogs and similar areas.
Floodplains are any areas of land susceptible to inundation by floodwaters from any source.
The 100-year floodplain is considered a Wetland Resource Area under the Wetlands Protection Act. Minimal 100-year floodplain still exists along the Charles River in Cambridge. However, the Alewife district, located in Cambridge, Arlington, and Belmont, consists of several hundred acres of sensitive ecological marshlands located entirely within the 100-year floodplain of the Alewife Brook.