A New Map Shows How Fast California’s Cliffs Are Collapsing

A new study measures which of the Golden State’s majestic seaside cliffs are falling fastest in order to come up with a plan

A new map made available through the Scripps Institution of Oceanography has brought to life researchers’ efforts to better predict which hotspots along the California coastline are most vulnerable to cliff collapse.

Adam Young of the Scripps Institution of Oceanography at UC San Diego and Zuzanna M. Swirad of the Polish Academy of Sciences in Warsaw based the map on their study of over 530 miles of California cliffs. Using advanced laser (lidar) datasets, the study provides insight into approximately 500 kilometers of previously unexamined coast, identifying northern California as a region with the highest cliff retreat rates.

“Understanding the rates and controls of cliff erosion,” the study reads, “is critical for building more resilient communities.”

Speaking to the Scripps Institution of Oceanography back in 2017, Young said he hoped that data such as this would “help improve models that predict erosion, help identify hazardous areas, and assist policymakers who are working to protect our coast.”

The study found that the rate of cliff collapse was more than 16 feet per year in places such as the Palos Verdes Peninsula, Big Sur, Point Arguello and Martins Beach just south of San Francisco, the Los Angeles Times reports, with the highest rates of erosion detected in Mendocino, Humboldt and Del Norte counties. Those hot spots include Usal Beach, the King Range, Centerville Beach—which are all part of a region known as the Lost Coast—and an area about two miles north of the Klamath River.

Along with potentially influencing policy, the study could also serve as an important tool to help the public contextualize the urgent hazard of cliff erosion. After all, part of what makes this erosion so dangerous is also what makes it so difficult to study. Change is episodic. Slow crumbling can give way to sudden catastrophic collapse, just as a period of large erosion can give way to the illusion of stabilization.

“It will mobilize again but we don’t know when,” Young explains.

This unpredictability is exacerbated by a number of environmental factors. The powerful crash of waves against a cliffside can make it not just picturesque but also incredibly difficult to measure—so too can a changing climate.

In an email to the San Francisco Chronicle, Swirad noted the need to identify relationships between erosion and waves, rain and rock hardness to better understand how erosion will unfold with the changing climate. This is further underscored by the fact that rising sea levels are expected to speed erosion rates, leaving highways, coastal property, power plants, beachgoers and more vulnerable to unexpected cliff collapse.

Lesley Ewing, a senior coastal engineer for the California Coastal Commission, cited the developing research as a potential “reality check for planners who often focus on specific regions and smaller scales.”

The consequences of this erosion are increasingly hard to dismiss. In 2019, three people died on a beach in Encinitas when a 30 foot chunk of cliff collapsed. This was followed by a 2021 collapse in Torrey Pines and a 2022 collapse in Del Mar.

Such devastation begs several questions: Is a walk on the beach a gamble? What does this erosion data mean for property owners? Where do we go from here?

As Young noted in 2020, in order to make better predictions about the future of California’s coastal cliffs we “need to understand what has happened in the past, what is happening right now, and why.”

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