Grand Isle, LA Coastal Erosion Rate
What USGS measures 15.1 miles southwest of Grand Isle, LA
Averaged across every transect USGS ran 15.1 miles southwest of Grand Isle, LA, the shoreline has been moving inland at 24.08 feet a year, a real measured rate, not a regional estimate applied to this stretch. At that rate, the shoreline has lost roughly 240.8 feet over the last decade.
What "Grand Isle" means on this page
Grand Isle, LA is the nearest named place, 15.1 miles away, to a ~3.5-mile stretch of coast USGS has surveyed - the reading below covers that whole stretch, not a single property in it. Segment center: 29.09, -90.24. USGS's Gulf of Mexico assessment last surveyed this stretch through 2001, computing the rate with its LRR method. Other US regions were surveyed in different years, sometimes decades apart, so this page states its own rather than implying one national vintage.
What 24.08 ft/yr means over time
Run 15.1 miles southwest of Grand Isle, LA's 24.08 ft/yr rate forward 25 years and it implies about 602 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 47 individual transects averaged together, 100% of which measured erosion rather than growth. Uncertainty on this specific number: 13.15 ft/yr either side. Sorted from fastest erosion to fastest growth across all 1211 measured segments nationally, this one lands at 4. Source: USGS Open-File Report 2004-1089. Rank 529 nationally for erosion belongs to Buellton, CA, 1794 miles from this stretch, measured at 0.18 ft/yr, a small fraction of this stretch's own rate. 2.5 miles away, Grand Isle, LA is the nearest other measured stretch: severe erosion at 17.17 ft/yr.
One address near Grand Isle: the Coastal Change Hazards Portal zooms past this stretch to the underlying map.