Dauphin Island, AL Coastal Erosion Rate
What USGS measures 13.2 miles east of Dauphin Island, AL
Good news, and an honest one: USGS's data can't distinguish this stretch, 13.2 miles east of Dauphin Island, AL, from a flat trend. Whatever small movement it measured here is statistical noise, not a reliable direction, so none is claimed.
What "Dauphin Island" 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 Dauphin Island, AL, rather than showing one arbitrary line. Segment center: 30.24, -87.95. Survey years: 2001, method LRR, from USGS's Gulf of Mexico 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 backs this reading up
This reading comes from 93 individual transects averaged together, 68% of which measured erosion rather than growth. Uncertainty on this specific number: 0.4 ft/yr either side. The unadjusted figure here, -0.14 ft/yr, would place it 574 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 2004-1089. For scale: Provincetown, MA, 1278 miles away, ranks 1129 of 1211 nationally for growth, 1.26 ft/yr. 3 miles away, Bon Secour, AL is the nearest other measured stretch: slight erosion at 0.39 ft/yr.
Dauphin Island, AL on the source map: try the Coastal Change Hazards Portal, zoomable well past this page's ~3.5-mile grain.