Grand Isle, LA Coastal Erosion Rate
What USGS measures 7.8 miles northeast of Grand Isle, LA
Good news, and an honest one: USGS's data can't distinguish this stretch, 7.8 miles northeast of Grand Isle, LA, from a flat trend. Whatever small movement it measured here is statistical noise, not a reliable direction, so none is claimed.
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: 29.30, -89.94. 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.
How solid is this number
Averaging 73 separate transects produced this segment's rate, with 95% individually reading as erosion, rather than relying on any single survey line. The published margin on this reading runs ±4.14 ft/yr. The unadjusted figure here, -1.44 ft/yr, would place it 163 of 1211 if ranked directly - but an unreliable rank isn't a useful one, which is exactly why "no significant trend" is the headline instead. Source: USGS Open-File Report 2004-1089. Rank 919 nationally for growth belongs to Smith River, CA, 2096 miles from this stretch, measured at 0.19 ft/yr. 2.5 miles up the coast, Grand Isle, LA shows 4.73 ft/yr of accreting.
One address near Grand Isle: the Coastal Change Hazards Portal zooms past this stretch to the underlying map.