South Duxbury, MA Coastal Erosion Rate
Is the coast eroding 4.2 miles east of South Duxbury, MA?
0.25 feet a year: that is the measured retreat rate USGS's transects show for the coast 4.2 miles east of South Duxbury, MA, averaged across the full historical record surveyed here. At that rate, the shoreline has lost roughly 2.5 feet over the last decade.
The grain of this number
Nothing here is parcel-level. USGS's raw transects run every few hundred feet along the shore; this page averages the ones nearest South Duxbury, MA into one ~3.5-mile reading rather than picking a single arbitrary line to represent the area. Centered near 42.01°N, 70.61°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 0.25 ft/yr holds for the next 25 years, the coast 4.2 miles east of South Duxbury, MA would retreat roughly 6 more feet, a projection, not a certainty: erosion rates shift with storms, sediment supply and any armoring built in the meantime.
What backs this reading up
65 transects feed this segment's number; 97% of them individually measured retreat. USGS's confidence interval here is ±0.24 ft/yr. Among the 1211 US coastal segments with a measurable trend, this one ranks 437 for erosion, 1 being the fastest-retreating coast in the dataset. Source: USGS Open-File Report 2010-1119. Rank 235 nationally for erosion belongs to Matagorda, TX, 1700 miles from this stretch, measured at 0.75 ft/yr, 3.0x this stretch's rate. South Duxbury, MA, 1.2 miles off, is the adjacent measured stretch, itself no significant trend.
Not this whole stretch, just South Duxbury itself: the Coastal Change Hazards Portal is USGS's own live version of this data.