Paia, HI Coastal Erosion Rate
What USGS measures 0.9 miles north of Paia, HI
The coast 0.9 miles north of Paia, HI has been retreating at a measured 0.27 feet a year, USGS's own long-term rate for this stretch, built from historical shoreline positions rather than a single survey. At that rate, the shoreline has lost roughly 2.7 feet over the last decade.
The grain of this number
This is a roughly 3.5-mile stretch of coast, not one address or parcel - USGS's own transects run every few hundred feet, but that's finer than any one property needs, so this page reports the stretch nearest Paia, HI. Centered near 20.92°N, 156.37°W. USGS's Hawaii assessment last surveyed this stretch through 2007-2010, computing the rate with its WLR method. Other US regions were surveyed in different years, sometimes decades apart, so this page states its own rather than implying one national vintage.
25 years at this rate
If 0.27 ft/yr holds for the next 25 years, the coast 0.9 miles north of Paia, HI would retreat roughly 7 more feet, a projection, not a certainty: erosion rates shift with storms, sediment supply and any armoring built in the meantime.
How solid is this number
38 transects feed this segment's number; 100% of them individually measured retreat. USGS's confidence interval here is ±0.24 ft/yr. Among the 1211 US coastal segments with a measurable trend, this one ranks 426 for erosion, 1 being the fastest-retreating coast in the dataset. Source: USGS Open-File Report 2011-1009. Rank 373 nationally for erosion belongs to Rockport, MA, 5042 miles from this stretch, measured at 0.35 ft/yr, 1.3x this stretch's rate. Paia, HI, 0.8 miles off, is the adjacent measured stretch, itself no significant trend.
Paia, HI on the source map: try the Coastal Change Hazards Portal, zoomable well past this page's ~3.5-mile grain.