Waimanalo Beach, HI Coastal Erosion Rate
Is the coast eroding 2.3 miles southeast of Waimanalo Beach, HI?
The coast 2.3 miles southeast of Waimanalo Beach, HI shows no statistically significant trend either way. USGS's transects measured a rate here, but it's smaller than the survey's own margin of error for this stretch, so calling it "eroding" or "growing" would overstate what the data actually shows.
What "Waimanalo Beach" means on this page
Nothing here is parcel-level. USGS's raw transects run every few hundred feet along the shore; this page averages the ones nearest Waimanalo Beach, HI into one ~3.5-mile reading rather than picking a single arbitrary line to represent the area. Centered near 21.31°N, 157.67°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.
How solid is this number
Averaging 81 separate transects produced this segment's rate, with 48% individually reading as erosion, rather than relying on any single survey line. USGS's confidence interval here is ±0.16 ft/yr. Taken at face value, this segment's raw 0 ft/yr reading would land it 773 of 1211 nationally - a number worth ignoring, since it's statistical noise rather than a real trend. Source: USGS Open-File Report 2011-1009. Rank 1043 nationally for growth belongs to Inwood, NY, 4961 miles from this stretch, measured at 0.59 ft/yr. East Honolulu, HI, 2.1 miles off, is the adjacent measured stretch, itself no significant trend.
One address near Waimanalo Beach: the Coastal Change Hazards Portal zooms past this stretch to the underlying map.