Study warns of mass beach erosion in Southern California

March 28, 2017

Beach erosion for La Jolla Shores predicted by the CoSMoS COAST model

A study published in a United States geophysics journal warns 31 to 67 percent of Southern California beaches could disappear by the year 2100 as a result of climate change.

The study uses a newly-developed computer model called Coastal Storm Modeling System — Coastal One-line Assimilated Simulation Tool (CosMoS-COAST) to predict shoreline change because of both sea level rise and changing storm patterns. The model factors in 3.3 to 6.5 feet of sea level rise and limited human intervention in predicting that about one third to two thirds of Southern California beaches would erode up to sea-cliffs or existing coastal infrastructure.

A press release issued by the American Geophysical Union, which published the study in its Journal of Geophysical Research: Earth Surface, states historical trends show 72 percent of Southern California beaches are getting larger. However, future projections show nearly all beaches will experience erosion as a result of accelerated sea-level rise.

Shoreline change is very hard to predict, the news release states. But, scientists are confident in the accuracy and reliability of the CosMoS-COAST model because of how it accurately reproduced the historical shoreline change between 1995 and 2010.

The lead author of the study, Sean Vitousek, said human efforts will be needed to preserve Southern California’s beaches. Vitousek was a post-doctoral fellow at the USGS at the time of the study and is currently a professor at the University of Illinois, Chicago in the the civil and materials engineering department.

“Beaches are perhaps the most iconic feature of California, and the potential for losing this identity is real,” Vitousek said. “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, business and homes to damage.”

Patrick Barnhard, a USGS geologist and coauthor of the study said massive and costly interventions will be necessary to preserve Southern California beaches.

“Beaches in Southern California are a crucial feature of the economy, and the first line of defense against coastal storm impacts of the 18 million residents in the region,” Barnhard said.

California Coastal Commission Executive Director John Ainsworth also weighed in on the study, saying the prospect of losing so many beaches to sea level rise is unacceptable.

“We must do everything we can to ensure that as much of the iconic California coast is preserved for future generations,” Ainsworth said.

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