A new report about sea level rise released by the U.S. Geological Survey on Monday includes dire predictions for beachgoers in Santa Barbara, Ventura, Los Angeles, Orange and San Diego counties — between 31 and 67 percent of Southern California beaches could become completely eroded in the next eight decades.
A newly developed computer model generated the predictions, shared with the public in a report entitled “Disappearing beaches: Modeling shoreline change in Southern California.”
The well-publicized massive erosion of Malibu’s Broad Beach may come to mind, but according to authors of the report, even beaches that have grown in the last century — many due to artificial nourishment projects — are predicted to shrink. In fact, the official summary of the study does not mince words: “Although a majority (72 percent) of beaches in Southern California show historical trends of accretion or getting larger (due to large artificial beach nourishments since the 1930s), future predictions indicate that nearly all of the beaches will experience erosion (will get smaller) due to accelerated sea-level rise.”
The model, years in the making, takes into account factors such as sand transport along the beach and across the beach by waves and sea-level drive, as well as historical shoreline positions and reactions of beaches to weather events such as El Niño.
“Beaches are perhaps the most iconic feature of California, and the potential for losing this identity is real,” Sean Vitousek, lead author of the study, said in an official statement. “The effect of California losing its beaches is not just a matter of affecting the tourism economy. Losing the protecting swath of beach sand between us and the pounding surf exposes critical infrastructure, businesses and homes to damage. Beaches are natural resources, and it is likely that human management efforts must increase in order to preserve them.” Vitousek was a post-doctoral fellow at the U.S. Geological Survey when he conducted the study and is now a professor at the University of Illinois at Chicago.
When it comes to Malibu-specific effects, an interactive map allows an adjustment of factors such as flooding, waves or flood potential, combined with amount of sea level rise (zero centimeters to two meters, with an option of an “extreme” rise at five meters) and an event, either “none,” an annual storm, a 20 year storm, a 100 year storm or a king tide. Although much of Malibu is safe from predicted rise levels from zero to 175 centimeters under dry conditions, areas of the Colony and Broad Beach appear under water, as well as sections of PCH at Trancas, Corral Canyon and Leo Carrillo State Beach during annual storm conditions at that level of ocean rise.
The map is available at usgs.gov/news/disappearing-beaches-modeling-shoreline-change-southern-california
Partners on the model include conservation-minded agencies such as the California Coastal Commission, California Coastal Conservancy, Caltrans, the National Park Service, NOAA Office for Coastal Management and several other agencies.