Rising sea level threatens Southern California beaches

Without expensive measures, some strands will vanish by 2100

Dusk surfing sessions at many Southern California beaches are at risk from sea level rise. @bberwyn photo.
Surfing El Granada in central California. @bberwyn photo.

Staff Report

Scientists are warily watching the impacts of rising sea levels along the world’s coastlines, where a high percentage of the global population lives and works. In some areas — especially narrow strands are pinned between the open ocean and coastal mountains, beaches may vanish by 2100 as higher waves and bigger storm surges wash away the precious sand.

Even with efforts to bolster them, between 31 percent and 67 percent of Southern California beaches may be completely eroded, scientists said this month after using a new climate model to calculate the effects of 3 to 6 feet of sea level rise.

“Beaches are perhaps the most iconic feature of California, and the potential for losing this identity is real,” said Sean Vitousek, who studied the region as part of a research project with the U.S. Geological Survey. “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,” said Vitousek, who  is now a professor in the Department of Civil & Materials Engineering at the University of Illinois at Chicago. The study is published in the Journal of Geophysical Research: Earth Surface, a publication of the American Geophysical Union.

Artificial measures bolstered many SoCal beaches since the 1930s, but the modeling shows that  nearly all of the beaches will shring due to accelerated sea-level rise.

The study suggests that “massive and costly interventions” will be needed to preseve the beaches, which are a crucial feature of the economy,and the first line of defense against coastal storm impacts for the 18 million residents in the region, according to USGS co-author Patrick Barnard.

The complex modeling includes calculations of sand transport both along the beach (due to longshore currents) and across the beach (cross-shore transport) by waves and sea-level rise, and can account for the topopgraphy of the SoCal coast, including  dunes, bluffs, cliffs, estuaries, river mouths, and urban infrastructure. Since it was able to accurately reconstruct shoreline changes of the past, the researchers are confident the model’s projections for the 2010-2100 period are accurate.

“The public already has to overcome obstacles in getting to the beach, from limited public transportation to illegally blocked pathways,” said California Coastal Commission Executive Director John Ainsworth. “The prospect of losing so many of our beaches in Southern California to sea level rise is frankly unacceptable. The beaches are our public parks and economic heart and soul of our coastal communities. We must do everything we can to ensure that as much of the iconic California coast is preserved for future generations.”

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