Dauphin Island, AL Coastal Erosion Rate
Is the coast eroding 8.7 miles east of Dauphin Island, AL?
The coast 8.7 miles east of Dauphin Island, AL shows no statistically significant trend either way. USGS's transects measured a rate here, but it's smaller than the survey's own margin of error for this stretch, so calling it "eroding" or "growing" would overstate what the data actually shows.
The grain of this number
Nothing here is parcel-level. USGS's raw transects run every few hundred feet along the shore; this page averages the ones nearest Dauphin Island, AL into one ~3.5-mile reading rather than picking a single arbitrary line to represent the area. Centered near 30.23°N, 88.03°W. The survey behind it runs to 2001, in USGS's Gulf of Mexico assessment, using the LRR method. Shoreline surveys aren't repeated every year, so this is the most recent long-term measurement USGS has published for this coast, not a live reading.
Where this fits nationally
4 transects feed this segment's number; 0% of them individually measured retreat. USGS's confidence interval here is ±2.96 ft/yr. Taken at face value, this segment's raw 0.38 ft/yr reading would land it 989 of 1211 nationally - a number worth ignoring, since it's statistical noise rather than a real trend. Source: USGS Open-File Report 2004-1089. For scale: Inwood, NY, 1070 miles away, ranks 1043 of 1211 nationally for growth, 0.59 ft/yr. Dauphin Island, AL, 1.6 miles off, is the adjacent measured stretch, itself no significant trend.
Not this whole stretch, just Dauphin Island itself: the Coastal Change Hazards Portal is USGS's own live version of this data.