Port St. Joe, FL Coastal Erosion Rate
What USGS measures 4.9 miles west of Port St. Joe, FL
0.51 feet a year: that is the measured retreat rate USGS's transects show for the coast 4.9 miles west of Port St. Joe, FL, averaged across the full historical record surveyed here. At that rate, the shoreline has lost roughly 5.1 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 Port St. Joe, FL into one ~3.5-mile reading rather than picking a single arbitrary line to represent the area. Centered near 29.80°N, 85.39°W. 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.
25 years at this rate
If 0.51 ft/yr holds for the next 25 years, the coast 4.9 miles west of Port St. Joe, FL would retreat roughly 13 more feet, a projection, not a certainty: erosion rates shift with storms, sediment supply and any armoring built in the meantime.
How solid is this number
This reading comes from 122 individual transects averaged together, 100% of which measured erosion rather than growth. USGS's confidence interval here is ±0.26 ft/yr. Among the 1211 US coastal segments with a measurable trend, this one ranks 297 for erosion, 1 being the fastest-retreating coast in the dataset. Source: USGS Open-File Report 2004-1089. Grand Isle, LA sits at national rank 16 for erosion (13.52 ft/yr), one reference point among the 1211 scored segments, 290 miles from here. 3 miles away, Port St. Joe, FL is the nearest other measured stretch: slight erosion at 0.53 ft/yr.
Not this whole stretch, just Port St. Joe itself: the Coastal Change Hazards Portal is USGS's own live version of this data.