Grand Isle, LA Coastal Erosion Rate
What USGS measures 10.6 miles southwest of Grand Isle, LA
Averaged across every transect USGS ran 10.6 miles southwest of Grand Isle, LA, the shoreline has been moving inland at 17.96 feet a year, a real measured rate, not a regional estimate applied to this stretch. At that rate, the shoreline has lost roughly 179.6 feet over the last decade.
What this reading actually covers
Grand Isle, LA is the nearest named place, 10.6 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: 29.12, -90.17. 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 17.96 ft/yr means over time
Run 10.6 miles southwest of Grand Isle, LA's 17.96 ft/yr rate forward 25 years and it implies about 449 feet of further retreat, assuming nothing changes, which is exactly the assumption a seawall or nourishment project exists to break.
Where this fits nationally
This reading comes from 19 individual transects averaged together, 100% of which measured erosion rather than growth. USGS's confidence interval here is ±2.94 ft/yr. Sorted from fastest erosion to fastest growth across all 1211 measured segments nationally, this one lands at 7. Source: USGS Open-File Report 2004-1089. Sargent, TX sits at national rank 72 for erosion (4.01 ft/yr), one reference point among the 1211 scored segments, 338 miles from here. 2 miles up the coast, Grand Isle, LA shows 13.52 ft/yr of eroding.
One address near Grand Isle: the Coastal Change Hazards Portal zooms past this stretch to the underlying map.