Marblehead, MA Coastal Erosion Rate
Is the coast eroding 0.8 miles west of Marblehead, MA?
Good news, and an honest one: USGS's data can't distinguish this stretch, 0.8 miles west of Marblehead, 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 Marblehead, MA, rather than showing one arbitrary line. Segment center: 42.50, -70.85. Survey years: 2007-2009, method LRR, from USGS's New England / Mid-Atlantic shoreline-change assessment. That's how current the data is here, real, but not a live feed, since a shoreline survey is a major undertaking, not an annual check-in.
Where this fits nationally
This reading comes from 34 individual transects averaged together, 100% of which measured erosion rather than growth. USGS's confidence interval here is ±0.18 ft/yr. The unadjusted figure here, -0.16 ft/yr, would place it 551 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. For scale: Pajaro Dunes, CA, 2697 miles away, ranks 1011 of 1211 nationally for growth, 0.45 ft/yr. Swampscott, MA, 2.6 miles off, is the adjacent measured stretch, itself no significant trend.
Not this whole stretch, just Marblehead itself: the Coastal Change Hazards Portal is USGS's own live version of this data.