Poipu, HI Coastal Erosion Rate
Is the coast eroding 0.9 miles southeast of Poipu, HI?
The coast 0.9 miles southeast of Poipu, HI has been retreating at a measured 0.32 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 3.2 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 Poipu, HI. Centered near 21.87°N, 159.45°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 0.32 ft/yr holds for the next 25 years, the coast 0.9 miles southeast of Poipu, HI would retreat roughly 8 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
Averaging 30 separate transects produced this segment's rate, with 93% individually reading as erosion, rather than relying on any single survey line. Uncertainty on this specific number: 0.31 ft/yr either side. Sorted from fastest erosion to fastest growth across all 1211 measured segments nationally, this one lands at 396. Source: USGS Open-File Report 2011-1009. For scale: Montauk, NY, 5119 miles away, ranks 523 of 1211 nationally for erosion, 0.18 ft/yr, 0.6x this stretch's rate. 0.6 miles away, Poipu, HI is the nearest other measured stretch: also no significant trend.
One address near Poipu: the Coastal Change Hazards Portal zooms past this stretch to the underlying map.