Siasconset, MA Coastal Erosion Rate
Is the coast eroding 5.9 miles north of Siasconset, MA?
USGS's shoreline-change data puts this stretch, 5.9 miles north of Siasconset, MA, at 1.33 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 13.3 feet over the last decade.
What "Siasconset" means on this page
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 Siasconset, MA, rather than showing one arbitrary line. Segment center: 41.34, -70.01. 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 1.33 ft/yr means over time
Run 5.9 miles north of Siasconset, MA's 1.33 ft/yr rate forward 25 years and it implies about 33 feet of further retreat, assuming nothing changes, which is exactly the assumption a seawall or nourishment project exists to break.
How solid is this number
This reading comes from 98 individual transects averaged together, 99% of which measured erosion rather than growth. USGS's confidence interval here is ±0.61 ft/yr. Among the 1211 US coastal segments with a measurable trend, this one ranks 173 for erosion, 1 being the fastest-retreating coast in the dataset. Source: USGS Open-File Report 2010-1119. Rank 373 nationally for erosion belongs to Rockport, MA, 94 miles from this stretch, measured at 0.35 ft/yr, 0.3x this stretch's rate. Nantucket, MA, 2 miles off, is the adjacent measured stretch, reading moderate erosion at 2 ft/yr.
Siasconset, MA on the source map: try the Coastal Change Hazards Portal, zoomable well past this page's ~3.5-mile grain.