Kahuku, HI Coastal Erosion Rate
Is the coast eroding 0.5 miles northwest of Kahuku, HI?
The coast 0.5 miles northwest of Kahuku, HI has been retreating at a measured 0.79 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 7.9 feet over the last decade.
What this reading actually covers
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 Kahuku, HI. Centered near 21.68°N, 157.95°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 0.79 ft/yr holds for the next 25 years, the coast 0.5 miles northwest of Kahuku, HI would retreat roughly 20 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
83 transects feed this segment's number; 100% of them individually measured retreat. Uncertainty on this specific number: 0.5 ft/yr either side. Sorted from fastest erosion to fastest growth across all 1211 measured segments nationally, this one lands at 224. Source: USGS Open-File Report 2011-1009. Rank 33 nationally for erosion belongs to Port St. Joe, FL, 4484 miles from this stretch, measured at 7.6 ft/yr, 9.6x this stretch's rate. Laie, HI, 2 miles off, is the adjacent measured stretch, itself no significant trend.
Not this whole stretch, just Kahuku itself: the Coastal Change Hazards Portal is USGS's own live version of this data.