Green Harbor, MA Coastal Erosion Rate
Is the coast eroding 1.3 miles south of Green Harbor, MA?
The coast 1.3 miles south of Green Harbor, MA has been retreating at a measured 0.44 feet a year, USGS's own long-term rate for this stretch, built from historical shoreline positions rather than a single survey. At that rate, the shoreline has lost roughly 4.4 feet over the last decade.
What "Green Harbor" means on this page
This is a roughly 3.5-mile stretch of coast, not one address or parcel - USGS's own transects run every few hundred feet, but that's finer than any one property needs, so this page reports the stretch nearest Green Harbor, MA. Centered near 42.05°N, 70.65°W. USGS's New England / Mid-Atlantic assessment last surveyed this stretch through 2007-2009, computing the rate with its LRR method. Other US regions were surveyed in different years, sometimes decades apart, so this page states its own rather than implying one national vintage.
25 years at this rate
If 0.44 ft/yr holds for the next 25 years, the coast 1.3 miles south of Green Harbor, MA would retreat roughly 11 more feet, a projection, not a certainty: erosion rates shift with storms, sediment supply and any armoring built in the meantime.
How solid is this number
This reading comes from 105 individual transects averaged together, 82% of which measured erosion rather than growth. The published margin on this reading runs ±0.17 ft/yr. This segment ranks 327 of 1211 measured US coastal segments, ordered from fastest erosion to fastest growth. Source: USGS Open-File Report 2010-1119. For scale: North Eastham, MA, 38 miles away, ranks 200 of 1211 nationally for erosion, 0.97 ft/yr, 2.2x this stretch's rate. 2.8 miles away, South Duxbury, MA is the nearest other measured stretch: also no significant trend.
One address near Green Harbor: the Coastal Change Hazards Portal zooms past this stretch to the underlying map.