Chatham, MA Coastal Erosion Rate
Is the coast eroding 5.5 miles south of Chatham, MA?
Averaged across every transect USGS ran 5.5 miles south of Chatham, MA, the shoreline has been moving inland at 4.33 feet a year, a real measured rate, not a regional estimate applied to this stretch. At that rate, the shoreline has lost roughly 43.3 feet over the last decade.
What "Chatham" means on this page
Chatham, MA is the nearest named place, 5.5 miles away, to a ~3.5-mile stretch of coast USGS has surveyed - the reading below covers that whole stretch, not a single property in it. Segment center: 41.60, -69.99. 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.
What 4.33 ft/yr means over time
Run 5.5 miles south of Chatham, MA's 4.33 ft/yr rate forward 25 years and it implies about 108 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
Averaging 86 separate transects produced this segment's rate, with 100% individually reading as erosion, rather than relying on any single survey line. USGS's confidence interval here is ±3.74 ft/yr. This segment ranks 66 of 1211 measured US coastal segments, ordered from fastest erosion to fastest growth. Source: USGS Open-File Report 2010-1119. Leggett, CA sits at national rank 337 for erosion (0.43 ft/yr), one reference point among the 1211 scored segments, 2778 miles from here. 2.3 miles away, Chatham, MA is the nearest other measured stretch: also no significant trend.
Not this whole stretch, just Chatham itself: the Coastal Change Hazards Portal is USGS's own live version of this data.