Scientists studying the California coastline found the volume of cliff material lost between 2016 and 2023 amounted to roughly 800 dump-truck loads for every yard of shoreline.

Researchers from UC San Diego’s Scripps Institution of Oceanography examined high-resolution aerial lidar surveys taken in 2026 and 2023 and found that much of this coastal cliff retreat was concentrated in hotspots in Northern and Central California, and included areas retreating more than 30 feet per year.

Previous cliff erosion rates were a decade old and the new analysis points to changes that are highly uneven across California’s coastline.

The researchers findings, published in the International Journal of Applied Earth Observation and Geoinformation, improve the understanding of California’s coastal geology and provide a framework for systematic statewide cliff monitoring.

Researchers estimate 70% of the California coast is made up of coastal cliffs. In addition to threatening coastal infrastructure and public resources, cliff collapse poses a serious threat to beachgoers, so monitoring erosion has become a priority for the state.

“The cliffs are not stable. They erode and collapse over time,” said Danghan Xie, an assistant professor and coastal geomorphologist at the University of Maryland and lead author of the study, who did the research while a postdoctoral scholar at Scripps. “We’ve seen many sad news stories about fatal cliff landslides. It’s unpredictable and a significant hazard to the coastal community.”

The rates of cliff top retreat vary along the shoreline with retreat hotspots mostly located in Central and Northern California, with some areas experiencing retreat rates exceeding 70 feet per year, such as the Lost Coast Headlands in Humboldt County where a landslide occurred involving over 1.4 million cubic yards of rock and soil, analysis showed.

“70 feet per year is a lot, over the seven-year study period that is more than the length of a football field,” said Adam Young, a coastal geomorphologist at Scripps and co-author of the new study and principal investigator of the project.

Cliff top retreat rates exceeding 10 feet per year were also observed in the King Range, Redwood National Park, Point Reyes National Seashore, Big Sur, near Martins Beach, Vandenberg Space Force Base, El Capitan State Beach, and Palos Verdes.

Statewide, 65% of cliffs showed a measurable change above the study thresholds.

Young and his colleagues have created a California Coastal Cliff Erosion Viewer website where all of this information is available to the public – one they plan to update as more information becomes available.

“This monitoring program is collecting lidar twice a year throughout the state of California, and we are using the data to update the rates on an annual and seasonal level,” said Young. “A detailed time series of cliff changes does not exist in many areas, and this makes it hard to build better predictive models. This project creates updated routine systematic data for improved coastal planning.”

Funding for the project ends in 2027.

Additional study authors include Luc Lenain, who was co-Principal Investigator, and Hironori Matsumoto of Scripps, and Zuzanna Swirad from the Polish Academy of Sciences. UC San Diego’s Scripps Institution of Oceanography.