Upper Grand Lagoon, FL Coastal Erosion Rate
Is the coast eroding 0.8 miles southeast of Upper Grand Lagoon, FL?
Good news, and an honest one: USGS's data can't distinguish this stretch, 0.8 miles southeast of Upper Grand Lagoon, FL, from a flat trend. Whatever small movement it measured here is statistical noise, not a reliable direction, so none is claimed.
What "Upper Grand Lagoon" 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 Upper Grand Lagoon, FL, rather than showing one arbitrary line. Segment center: 30.16, -85.74. The survey behind it runs to 2001, in USGS's Gulf of Mexico assessment, using the LRR method. Shoreline surveys aren't repeated every year, so this is the most recent long-term measurement USGS has published for this coast, not a live reading.
How solid is this number
72 transects feed this segment's number; 42% of them individually measured retreat. Uncertainty on this specific number: 0.34 ft/yr either side. The unadjusted figure here, 0.02 ft/yr, would place it 790 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. Stone Harbor, NJ sits at national rank 1069 for growth (0.73 ft/yr), one reference point among the 1211 scored segments, 875 miles from here. 2 miles up the coast, Upper Grand Lagoon, FL shows the same lack of a significant trend.
Not this whole stretch, just Upper Grand Lagoon itself: the Coastal Change Hazards Portal is USGS's own live version of this data.