Grand Isle, LA Coastal Erosion Rate
What USGS measures 19.3 miles southwest of Grand Isle, LA
USGS's shoreline-change data puts this stretch, 19.3 miles southwest of Grand Isle, LA, at 19.03 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 190.3 feet over the last decade.
The grain of this number
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: 29.07, -90.31. 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 19.03 ft/yr means over time
Run 19.3 miles southwest of Grand Isle, LA's 19.03 ft/yr rate forward 25 years and it implies about 476 feet of further retreat, assuming nothing changes, which is exactly the assumption a seawall or nourishment project exists to break.
Where this fits nationally
10 transects feed this segment's number; 100% of them individually measured retreat. Uncertainty on this specific number: 18.91 ft/yr either side. Sorted from fastest erosion to fastest growth across all 1211 measured segments nationally, this one lands at 6. Source: USGS Open-File Report 2004-1089. Rank 16 nationally for erosion belongs to Grand Isle, LA, 11 miles from this stretch, measured at 13.52 ft/yr, 0.7x this stretch's rate. 1.3 miles away, Grand Isle, LA is the nearest other measured stretch: severe erosion at 21.03 ft/yr.
One address near Grand Isle: the Coastal Change Hazards Portal zooms past this stretch to the underlying map.