Grand Isle, LA Coastal Erosion Rate
Shoreline change 18 miles southwest of Grand Isle, LA
USGS's shoreline-change data puts this stretch, 18 miles southwest of Grand Isle, LA, at 21.03 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 210.3 feet over the last decade.
What "Grand Isle" 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 Grand Isle, LA, rather than showing one arbitrary line. Segment center: 29.08, -90.29. 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 21.03 ft/yr means over time
Run 18 miles southwest of Grand Isle, LA's 21.03 ft/yr rate forward 25 years and it implies about 526 feet of further retreat, assuming nothing changes, which is exactly the assumption a seawall or nourishment project exists to break.
How solid is this number
This reading comes from 19 individual transects averaged together, 100% of which measured erosion rather than growth. The published margin on this reading runs ±19.76 ft/yr. Among the 1211 US coastal segments with a measurable trend, this one ranks 5 for erosion, 1 being the fastest-retreating coast in the dataset. Source: USGS Open-File Report 2004-1089. For scale: Hampton Bays, NY, 1289 miles away, ranks 312 of 1211 nationally for erosion, 0.46 ft/yr, a small fraction of this stretch's own rate. Grand Isle, LA, 1.3 miles off, is the adjacent measured stretch, reading severe erosion at 19.03 ft/yr.
One address near Grand Isle: the Coastal Change Hazards Portal zooms past this stretch to the underlying map.