Southern California’s beaches have increased in size by more than 500 acres over the past four decades, according to a study led by researchers from the University of California, Irvine, the U.S. Geological Survey (USGS), and other organizations. The findings were published in Nature Communications.
The research analyzed shoreline changes across California from 1984 to 2024 using new satellite-derived measurement techniques. The results show that Southern California’s beaches expanded by about 10 percent during this period, even though dams and urban development were expected to limit sediment flow and cause erosion.
“This is a counterintuitive finding considering previous reports of widespread beach erosion in Southern California,” said Brett Sanders, UC Irvine professor of civil and environmental engineering. “While several individual beaches did experience severe erosion, there were also several that experienced dramatic widening, and the overall trend shows widening at an average rate of 7.2 meters across 320 kilometers of Southern California coastline.”
The study found that nearly half—49 percent—of the shoreline widened significantly while 31 percent narrowed. Some areas such as Zuma near Malibu and northern Oceanside littoral cells experienced severe erosion, with narrowing rates exceeding one meter per year leading to property damage.
Beach growth has been concentrated at human-made coastal structures like harbors and jetties or natural convergence zones where sediment accumulates. Rapidly growing locations include Huntington Beach, Santa Monica, and stretches between Ventura and Oxnard.
The research examined three regions: northern, central, and southern California. Southern California showed strong positive trends in beach area; Northern California had moderate growth; Central California showed no significant change.
“The primary challenge facing Southern California beaches is not sediment shortage, but sediment distribution,” said Jonathan Warrick, lead author and USGS research geologist at the Pacific Coastal and Marine Science Center in Santa Cruz. “Some of the most rapidly widening beaches – including McGrath State Beach, Huntington Beach, and Venice Beach – now measure approximately 200 meters, or over 600 feet wide. These locations benefit from sediment trapped by coastal structures or accumulating in natural sand convergence zones.”
Researchers used newly developed satellite data with advanced signal-processing methods for higher accuracy compared to earlier approaches relying on limited historical snapshots.
“These new tools are revolutionizing how we assess beaches and their changes,” Sanders said. “Beaches were previously monitored by field crews using surveying equipment or with aerial flights that scan the coast with laser surveys, but the costs of these approaches limited the frequency and spatial extent of available data. Satellite imagery now allows us to measure beach width everywhere, several times per month.”
The findings suggest opportunities for better coastal management through redistribution rather than addition of new sediment sources. Existing programs at some harbors move sand around barriers such as jetties; expanding these efforts could make use of existing resources more broadly along the coast.
For example, in the San Pedro littoral cell—including Sunset Beach, Huntington Beach, and Newport Beach—beach engineering projects led to an average expansion of 25 meters (over 80 feet) during the study period.
Although large dams have reduced sand supply to about half its historical level statewide due to land use changes (https://www.usgs.gov/programs/cmhrp/news/new-study-finds-california-beaches-are-growing-despite-urbanization-and-dams), other sources like bluff erosion or artificial sand additions have helped sustain or grow many beaches.
Despite these opportunities for improved management practices using modern data collection methods (https://newsroom.ucla.edu/releases/california-beaches-grow-in-size-satellite-data), challenges remain such as financial costs, regulatory requirements, institutional inertia across political boundaries—and resistance to changing established practices.
“These data give us a much-needed systems perspective of beach dynamics making it easier to find entry points required for effective management,” Sanders said.
Co-authors included Kilian Vos (OHB Digital Services), Daniel Buscombe (Washington Department of Ecology), Andrew Ritchie and Sean Vidousek (USGS), Teresa Hachey (UC Irvine). Funding was provided by USGS and NASA.
