Two new studies from researchers at UC San Diego's Scripps Institution of Oceanography provide encouraging news about California's beaches at both local and statewide scales.
The 2025 San Diego County Beach Report found most beaches in the region grew in width last year as beaches entered a post-El Niño recovery phase, while a companion study published in Nature Communications discovered that California's average beach width has remained remarkably stable across nearly four decades despite notable examples of beach erosion.
San Diego County Beach Report 2025
The San Diego County Beach Report is a monitoring effort conducted by the Scripps Coastal Processes Group and funded by California State Parks that tracks beach erosion or expansion in the region. The report encompasses nine San Diego County beaches: Carlsbad State Beach, South Carlsbad State Beach, Leucadia State Beach, Moonlight State Beach, San Elijo State Beach, Cardiff State Beach, Torrey Pines State Beach, Silver Strand State Beach and Border Field State Park. Some of these beaches have been continuously monitored for more than 20 years.
"Tracking beach width is important because beaches are our first defense against flooding on our coastline," said Adam Young, a coastal geomorphologist at Scripps who co-authored the report. "Healthy beaches are also very important for recreation, cultural and economic reasons."
To create the beach report, researchers collect 3D measurements of the nine beaches at least once a month using a LiDAR (Light Detection and Ranging) scanner attached to either a truck, ATV or drone. LiDAR works by firing a laser thousands of times per second and measuring the time it takes for the beams to bounce off objects and return to the sensor. The mobile LiDAR instrumentation used in this study was purchased using Community Project Funding supported by U.S. Rep. Mike Levin (CA-49). This year's beach report features measurements taken between Oct 1, 2024 to Sep 30, 2025.
Managers at California State Parks use the beach report data to track beach health.
"Being able to look across multiple years of the beach report lets managers assess trends, which can help inform decisions about potential beach nourishment projects," said Mark Merrifield, one of the study's co-authors and director of the Scripps Center For Climate Change Impacts and Adaptation . "On the flip side, our research also establishes that multi-year cycles of widening or narrowing beaches are not unusual. Multiple years of beach recovery often occur after a strong erosion year."
California beaches usually lose width during El Niño years, because the larger, more powerful waves associated with El Niño years in California rip sand from beaches and carry it offshore. The intervening years between El Niños are usually times when beaches recover some of that lost width.
So, the 2025 San Diego County Beach Report's finding that most beaches gained width last year is the start of what researchers expect to be a recovery period.
"The good news is that we are now officially in the beach recovery phase post-El Niño," said William O'Reilly, an oceanographer at Scripps and the report's lead author. "That said, the last recovery phase didn't go too well, so we need to wait and see if beaches continue to recover or if it will be spoiled by increased atmospheric river activity or other extreme weather events."
The last expected recovery period between the El Niños of 2016 and 2024 resulted in most San Diego beaches losing width each year following the 2016 El Niño through the end of the 2023-2024 winter. This happened because several of the winters during this time frame produced strong waves despite not being El Niño years — including the atmospheric rivers of the 2022-2023 winter and an extreme wave event in 2021 .
The 2023-2024 El Niño ended up not sending a lot of wave energy to the U.S. West Coast and researchers hope San Diego beaches will continue to add width for the next three to five years until the next expected El Niño.
The report's authors also said some of the recent increase in beach width measured by the researchers was due to beach nourishment projects in Encinitas and Solana Beach. The sand added for each of those projects has been generally migrating south.
Researchers say there isn't yet a clear signal of increased or decreased beach erosion in San Diego County that might be attributable to higher global average temperatures. However, the report's authors said such a trend might emerge if accurate records of beach widths extended farther back in time.
Statewide stability
This absence of a clear trend at the local level was also echoed by a statewide study, funded by the U.S. Army Corps of Engineers, California State Parks and the Office of Naval Research, that was also led by O'Reilly. The study found the average beach width for the state of California had remained roughly the same across nearly four decades. Researchers used images collected by the NASA and United States Geological Survey's Landsat satellites to track changes in beach width across the entire state of California from 1985 to 2021. To do this the team used a software toolkit called CoastSat that detects changes in shoreline position, defined as where the ocean meets dry sand, for sand or gravel coastlines in satellite imagery. The study excluded rocky coasts, ocean cliffs or other places without beaches.
The findings were a surprise to the research team because of the well-documented reduction in sediment supplied by California's rivers, many of which have been dammed or diverted, and because of specific beaches that have shown long-term narrowing trends.
"Among California's beaches there have been winners and losers over the past 40 years or so, but across the whole state those wins and losses seem to even out," said O'Reilly. "Some places are experiencing significant erosion and likely will continue to, but there are other nearby places gaining sand. The deck is being reshuffled and redistributed a bit along the California coastline, and we don't yet fully understand what's driving that reshuffling."
Some of the "winners" include the south end of the beach at Camp Pendleton near San Diego, Venice Beach in Los Angeles and the north end of Ocean Beach in San Francisco. Beaches losing sand include places such as Oceanside and San Clemente.
While future sea-level rise is likely to complicate this picture even further, O'Reilly said the unexpected findings were encouraging.
"Our beaches showed more natural resilience than we were expecting," he said. "Even after a strong El Niño year, our jetski surveys in San Diego show the majority of the sand hasn't left the system. Sometimes the sand is parked a quarter mile offshore, but it can make its way back after three or four years with the right conditions."
Together, these two pieces of research provide immediate and long-term perspectives on California's coastal resilience. The San Diego County Beach Report tracks local changes essential for management decisions, while the statewide analysis reveals surprising stability. The findings of each study show how dynamic California's beaches are, and provide precious information that can help managers and policymakers better understand coastal erosion.
In addition to O'Reilly, Merrifield and Young, Michele Okihiro, Mele Johnson, Brian Woodward, Jon Curtis and Lucian Parry of Scripps co-authored the 2025 San Diego County Beach Report.
Additional co-authors for the Nature Communications study include Dayeon Yoon, Holden Leslie-Bole and Robert Guza of Scripps as well as Laura Cagigal of Universidad de Cantabria, Susheel Adusumilli of the University of Oregon and Kilian Vos of OHB Digital Services.
