Half Moon Bay, CA Coastal Erosion Rate
Is the coast eroding 1.1 miles south of Half Moon Bay, CA?
Good news, and an honest one: USGS's data can't distinguish this stretch, 1.1 miles south of Half Moon Bay, CA, 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 Half Moon Bay, CA, rather than showing one arbitrary line. Segment center: 37.45, -122.44. The survey behind it runs to 1852-2016, in USGS's California assessment, using the LRR method. Shoreline surveys aren't repeated every year, so this is the most recent long-term measurement USGS has published for this coast, not a live reading.
Where this fits nationally
101 transects feed this segment's number; 57% of them individually measured retreat. The published margin on this reading runs ±0.2 ft/yr. The unadjusted figure here, -0.04 ft/yr, would place it 735 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 National Shoreline Change data release (ScienceBase, DOI 10.5066/P94J0K7Z), Kratzmann 2024 / Data Report 1187. Rank 1069 nationally for growth belongs to Stone Harbor, NJ, 2560 miles from this stretch, measured at 0.73 ft/yr. El Granada, CA, 2.7 miles off, is the adjacent measured stretch, itself no significant trend.
Half Moon Bay, CA on the source map: try the Coastal Change Hazards Portal, zoomable well past this page's ~3.5-mile grain.