Chatham, MA Coastal Erosion Rate
What USGS measures 8.1 miles south of Chatham, MA
Unusual good news for this stretch: the shoreline 8.1 miles south of Chatham, MA has grown by a measured 5.4 feet a year on average, per USGS's long-term transect data for this section. At that rate, the shoreline has gained roughly 54 feet over the last decade.
The grain of this number
Nothing here is parcel-level. USGS's raw transects run every few hundred feet along the shore; this page averages the ones nearest Chatham, MA into one ~3.5-mile reading rather than picking a single arbitrary line to represent the area. Centered near 41.56°N, 70.00°W. 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.
25 years at this rate
Holding the 5.4 ft/yr accretion rate 8.1 miles south of Chatham, MA for 25 years would add roughly 135 feet of shoreline, again assuming nothing about the local sediment supply changes.
What backs this reading up
93 transects feed this segment's number; 20% of them individually measured retreat. Uncertainty on this specific number: 1.33 ft/yr either side. Sorted from fastest erosion to fastest growth across all 1211 measured segments nationally, this one lands at 1203. Source: USGS Open-File Report 2010-1119. Rank 1024 nationally for growth belongs to Camp Pendleton South, CA, 2632 miles from this stretch, measured at 0.49 ft/yr, a small fraction of this stretch's own rate. 2.6 miles away, Chatham, MA is the nearest other measured stretch: severe erosion at 4.33 ft/yr.
Not this whole stretch, just Chatham itself: the Coastal Change Hazards Portal is USGS's own live version of this data.