South Duxbury, MA Coastal Erosion Rate
Shoreline change 3 miles east of South Duxbury, MA
Good news, and an honest one: USGS's data can't distinguish this stretch, 3 miles east of South Duxbury, MA, from a flat trend. Whatever small movement it measured here is statistical noise, not a reliable direction, so none is claimed.
The grain of this number
USGS surveys the coast in transects spaced a few hundred feet apart; this page groups the nearest ones into a single ~3.5-mile reading for the stretch closest to South Duxbury, MA, rather than showing one arbitrary line. Segment center: 42.01, -70.63. The survey behind it runs to 2007-2009, in USGS's New England / Mid-Atlantic assessment, using the LRR method. Shoreline surveys aren't repeated every year, so this is the most recent long-term measurement USGS has published for this coast, not a live reading.
What backs this reading up
79 transects feed this segment's number; 80% of them individually measured retreat. Uncertainty on this specific number: 0.23 ft/yr either side. The unadjusted figure here, -0.14 ft/yr, would place it 576 of 1211 if ranked directly - but an unreliable rank isn't a useful one, which is exactly why "no significant trend" is the headline instead. Source: USGS Open-File Report 2010-1119. Santiago, WA sits at national rank 1143 for growth (1.54 ft/yr), one reference point among the 1211 scored segments, 2607 miles from here. 1.2 miles up the coast, South Duxbury, MA shows 0.25 ft/yr of eroding.
South Duxbury, MA on the source map: try the Coastal Change Hazards Portal, zoomable well past this page's ~3.5-mile grain.