Grand Isle, LA Coastal Erosion Rate
Is the coast eroding 10.7 miles northeast of Grand Isle, LA?
8.55 feet a year: that is the measured retreat rate USGS's transects show for the coast 10.7 miles northeast of Grand Isle, LA, averaged across the full historical record surveyed here. At that rate, the shoreline has lost roughly 85.5 feet over the last decade.
What "Grand Isle" means on this page
Nothing here is parcel-level. USGS's raw transects run every few hundred feet along the shore; this page averages the ones nearest Grand Isle, LA into one ~3.5-mile reading rather than picking a single arbitrary line to represent the area. Centered near 29.32°N, 89.90°W. 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.
25 years at this rate
If 8.55 ft/yr holds for the next 25 years, the coast 10.7 miles northeast of Grand Isle, LA would retreat roughly 214 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
Averaging 48 separate transects produced this segment's rate, with 100% individually reading as erosion, rather than relying on any single survey line. Uncertainty on this specific number: 3.27 ft/yr either side. This segment ranks 27 of 1211 measured US coastal segments, ordered from fastest erosion to fastest growth. Source: USGS Open-File Report 2004-1089. Rank 155 nationally for erosion belongs to Bolivar Peninsula, TX, 272 miles from this stretch, measured at 1.55 ft/yr, 0.2x this stretch's rate. Grand Isle, LA, 1.8 miles off, is the adjacent measured stretch, reading severe erosion at 8.55 ft/yr.
Not this whole stretch, just Grand Isle itself: the Coastal Change Hazards Portal is USGS's own live version of this data.