Thursday November 20, 2025
SFGATE —
Studies on California beaches often highlight their dirtiness or the fact that they’re disappearing altogether. But a recent study from UC San Diego’s Scripps Institution of Oceanography found some rare encouraging data about the state’s shoreline.
Using satellite imaging from 1985 to 2021, Scripps found that California beaches have remained relatively stable in width, according to a new study published in Nature. That’s a surprising finding, given the prevailing narrative that erosion is causing the state’s beaches to shrink every year.
“The general consensus had been within the state that we were probably losing sand,” said William O’Reilly, an oceanographer at Scripps and the report’s lead author.
He rattled off several reasons: Rivers had been dammed, preventing the sediment flow that replenishes beaches; there had been several strong El Niño years with intense storms that ripped sand offshore; and coastal armoring like seawalls was prevalent.
“There are notable differences, and every beach is a different story,” O’Reilly said of the report, “but yeah, taken as a whole, what we found was remarkable.”
Many California beaches have eroded significantly, but others have seen the amount of sand increase, offsetting any overall declines in beach width across the state. “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,” O’Reilly told UC San Diego.
The study, funded by the U.S. Army Corps of Engineers, the California Department of Parks and Recreation, and the Office of Naval Research, also acknowledged ongoing beach nourishment projects — the act of manually adding sand to beaches — that have helped to stabilize areas of coastline. But the authors noted that given the number of projects along the coast in that time period, “it can’t be having a huge influence on this bigger story,” O’Reilly said.
The overall scale of beach nourishment projects, when compared with the entire coastline, is also small. Beach nourishment is much more common on Southern California beaches than in Northern California.
The study identified some of California’s “winners and losers.” The beaches of San Francisco and Venice, for example, fared much better than beaches in cities such as San Clemente and Oceanside.
The story is also ongoing. The years since 2021, which weren’t included in the study, have seen multiple extreme weather events that have damaged the coastline, battering historic piers and causing local flooding. O’Reilly said the researchers have already seen that the recovery of California beaches in this post-El Niño period has been less productive than in previous years. Beaches typically lose sand in El Niño years and then recover in the years following.
O’Reilly said that 36 years — the duration of the study — may seem like a long, significant period to analyze, but it’s not that long in terms of natural climate variation. The next 36 years could look very different. The researchers would ideally like to look at data that’s at least double that to really understand climate cycles, he said, and those longer sets of data will be what can help policymakers decide what to do in the face of beach erosion in the future.
“It’s not close to being long enough to address some of the fundamental climate questions,” O’Reilly said.