Olowalu, HI Coastal Erosion Rate
What USGS measures 2 miles southeast of Olowalu, HI
Good news, and an honest one: USGS's data can't distinguish this stretch, 2 miles southeast of Olowalu, HI, from a flat trend. Whatever small movement it measured here is statistical noise, not a reliable direction, so none is claimed.
The grain of this number
USGS surveys the coast in transects spaced a few hundred feet apart; this page groups the nearest ones into a single ~3.5-mile reading for the stretch closest to Olowalu, HI, rather than showing one arbitrary line. Segment center: 20.80, -156.60. 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.
How solid is this number
296 transects feed this segment's number; 96% of them individually measured retreat. The published margin on this reading runs ±0.22 ft/yr. The unadjusted figure here, -0.19 ft/yr, would place it 512 of 1211 if ranked directly - but an unreliable rank isn't a useful one, which is exactly why "no significant trend" is the headline instead. Source: USGS Open-File Report 2011-1009. Rank 1190 nationally for growth belongs to Copalis Beach, WA, 2566 miles from this stretch, measured at 3.87 ft/yr. 2 miles away, Olowalu, HI is the nearest other measured stretch: also no significant trend.
Not this whole stretch, just Olowalu itself: the Coastal Change Hazards Portal is USGS's own live version of this data.