Captiva, FL Coastal Erosion Rate
What USGS measures 1.5 miles southeast of Captiva, FL
USGS's shoreline-change data puts this stretch, 1.5 miles southeast of Captiva, FL, at 2.34 feet of erosion a year on average, a long-term rate for this specific ~3.5-mile section, not one storm's damage. At that rate, the shoreline has lost roughly 23.4 feet over the last decade.
The grain of this number
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 Captiva, FL, rather than showing one arbitrary line. Segment center: 26.48, -82.17. 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 2.34 ft/yr means over time
Run 1.5 miles southeast of Captiva, FL's 2.34 ft/yr rate forward 25 years and it implies about 59 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
44 transects feed this segment's number; 82% of them individually measured retreat. The published margin on this reading runs ±1.52 ft/yr. This segment ranks 113 of 1211 measured US coastal segments, ordered from fastest erosion to fastest growth. Source: USGS Open-File Report 2004-1089. Rank 127 nationally for erosion belongs to Edgartown, MA, 1221 miles from this stretch, measured at 2.13 ft/yr, 0.9x this stretch's rate. Captiva, FL, 1.9 miles off, is the adjacent measured stretch, itself no significant trend.
Not this whole stretch, just Captiva itself: the Coastal Change Hazards Portal is USGS's own live version of this data.