Why USGS's Coastal Surveys Are a Different Age in Every Region

Not one national survey date

USGS's shoreline-change assessment was never run as a single national survey - each region was studied separately, on its own timeline, using whatever historical shoreline sources (old topographic surveys, aerial photos, lidar) existed for that coast. The result is a genuinely different vintage per region, and CoastErosionCheck states each segment's own rather than implying a single national "as of" date.

The actual spread

Gulf of Mexico data runs through 2001. New England and Mid-Atlantic surveys are from 2007-2009. The Pacific Northwest spans 2002-2011. Hawaii's assessment runs 2007-2010. California's is the widest: some of its historical shoreline positions go back to 1852, with the long-term rate calculated through as recently as 2016.

What this means for a reading today

A rate labeled "long-term" describes the trend USGS measured up to that survey's own end date, not a live feed. Coastlines can and do change after a survey's cutoff, especially after a major storm, so a segment's own vintage line is worth reading before treating a rate as current.

Why USGS hasn't re-surveyed everything since

A shoreline-change assessment is a major undertaking - digitizing decades of historical shoreline positions per transect, not a satellite check-in - which is why regions are updated on a timescale of years to decades rather than annually. CoastErosionCheck will reflect a newer USGS release for any region if and when one is published.

Where to go next

See the range this plays out across: Golden Meadow, LA, Dauphin Island, AL, Ocean Shores, WA.

Why Some US Coastline Is Growing, Not Eroding · How CoastErosionCheck Calculates a Coast's Erosion Rate