Nantucket, MA Coastal Erosion Rate
Shoreline change 1.7 miles south of Nantucket, MA
USGS's shoreline-change data puts this stretch, 1.7 miles south of Nantucket, MA, at 0.8 feet of erosion a year on average, a long-term rate for this specific ~3.5-mile section, not one storm's damage. At that rate, the shoreline has lost roughly 8 feet over the last decade.
What this reading actually covers
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 Nantucket, MA, rather than showing one arbitrary line. Segment center: 41.25, -70.10. 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.
What 0.8 ft/yr means over time
Run 1.7 miles south of Nantucket, MA's 0.8 ft/yr rate forward 25 years and it implies about 20 feet of further retreat, assuming nothing changes, which is exactly the assumption a seawall or nourishment project exists to break.
What backs this reading up
This reading comes from 87 individual transects averaged together, 64% of which measured erosion rather than growth. The published margin on this reading runs ±0.75 ft/yr. Among the 1211 US coastal segments with a measurable trend, this one ranks 222 for erosion, 1 being the fastest-retreating coast in the dataset. Source: USGS Open-File Report 2010-1119. Grand Isle, LA sits at national rank 38 for erosion (6.6 ft/yr), one reference point among the 1211 scored segments, 1397 miles from here. 2.6 miles away, Madaket, MA is the nearest other measured stretch: moderate erosion at 2.69 ft/yr.
Not this whole stretch, just Nantucket itself: the Coastal Change Hazards Portal is USGS's own live version of this data.