Bellport, NY Coastal Erosion Rate
Is the coast eroding 3.4 miles southeast of Bellport, NY?
Averaged across every transect USGS ran 3.4 miles southeast of Bellport, NY, the shoreline has been moving inland at 0.56 feet a year, a real measured rate, not a regional estimate applied to this stretch. At that rate, the shoreline has lost roughly 5.6 feet over the last decade.
What this reading actually covers
Bellport, NY is the nearest named place, 3.4 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: 40.73, -72.88. 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 0.56 ft/yr means over time
Run 3.4 miles southeast of Bellport, NY's 0.56 ft/yr rate forward 25 years and it implies about 14 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 31 individual transects averaged together, 100% of which measured erosion rather than growth. Uncertainty on this specific number: 0.2 ft/yr either side. This segment ranks 282 of 1211 measured US coastal segments, ordered from fastest erosion to fastest growth. Source: USGS Open-File Report 2010-1119. For scale: Virginia Beach, VA, 319 miles away, ranks 249 of 1211 nationally for erosion, 0.65 ft/yr, 1.2x this stretch's rate. Bellport, NY, 1.4 miles off, is the adjacent measured stretch, reading slight erosion at 0.56 ft/yr.
Not this whole stretch, just Bellport itself: the Coastal Change Hazards Portal is USGS's own live version of this data.