Big Lagoon, CA Coastal Erosion Rate
What USGS measures 3.3 miles southwest of Big Lagoon, CA
USGS's shoreline-change data puts this stretch, 3.3 miles southwest of Big Lagoon, CA, at 0.55 feet of erosion a year on average, a long-term rate for this specific ~3.5-mile section, not one storm's damage. At that rate, the shoreline has lost roughly 5.5 feet over the last decade.
What "Big Lagoon" means on this page
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 Big Lagoon, CA, rather than showing one arbitrary line. Segment center: 41.12, -124.16. Survey years: 1852-2016, method LRR, from USGS's California shoreline-change assessment. That's how current the data is here, real, but not a live feed, since a shoreline survey is a major undertaking, not an annual check-in.
What 0.55 ft/yr means over time
Run 3.3 miles southwest of Big Lagoon, CA's 0.55 ft/yr rate forward 25 years and it implies about 14 feet of further retreat, assuming nothing changes, which is exactly the assumption a seawall or nourishment project exists to break.
What backs this reading up
This reading comes from 24 individual transects averaged together, 100% of which measured erosion rather than growth. USGS's confidence interval here is ±0.43 ft/yr. Among the 1211 US coastal segments with a measurable trend, this one ranks 286 for erosion, 1 being the fastest-retreating coast in the dataset. Source: USGS National Shoreline Change data release (ScienceBase, DOI 10.5066/P94J0K7Z), Kratzmann 2024 / Data Report 1187. For scale: Carmel Valley Village, CA, 356 miles away, ranks 264 of 1211 nationally for erosion, 0.61 ft/yr, 1.1x this stretch's rate. Big Lagoon, CA, 2.9 miles off, is the adjacent measured stretch, itself no significant trend.
Not this whole stretch, just Big Lagoon itself: the Coastal Change Hazards Portal is USGS's own live version of this data.