Environment Report: Cliff Dangers Are Clear But the Causes Aren't - Voice of San Diego

Science/Environment UNVEILING THE UNSEEN

Environment Report: Cliff Dangers Are Clear But the Causes Aren't

A Scripps Institution of Oceanography researcher who studies coastal erosion says it’s nearly impossible to pinpoint the cause of cliff collapses like the one that killed three people in Encinitas on Friday.

A warning sign is posted near the site of a deadly cliff collapse in Encinitas. / Image via Shutterstock

In 1938, the yoga teacher Paramahansa Yogananda dedicated the Golden Lotus Temple along the Encinitas coast.

As an impending cliff collapse became clear just a few years later, Yogananda — also known as Swami and for whom a famous surf spot is named — was tempted to hold a last service in the temple but decided not to risk the lives of his congregation.

In 1942, the collapse happened. The old temple, teetering on the side of the fallen bluff, was removed.

Decades later, a pool at Swami’s is left empty, a reverend there told the Union-Tribune, because of worries the water would be too much weight and could contribute to another landslide.

Others have not been as judicious. In the decades since the temple slid off the cliff, more houses have been built along the coast, altering the landscape and, perhaps, endangering those who live there and below.

Of course, erosion has happened long before humans started building houses along the ocean. It’s caused primarily by wind and water. Some water is natural — waves and runoff, for instance. Other water is unnatural, like leaking water systems that weaken the ground, or the rising seas caused by human-made climate change.

On Friday, the catastrophic consequences of cliff collapses again became clear when a bluff near Encinitas collapsed and killed three people.

Earlier this year, I spoke with Adam Young, a Scripps Institution of Oceanography researcher who studies coastal erosion. If you’ve read any articles on the recent bluff collapse, you’ve probably seen Young say cliff failures have several causes and that he can’t speculate on why the cliffs near Encinitas fell when they did.

“Technically, all cliffs are eroding,” he told me at the time.

Indeed, one of Young’s key findings is sure to frustrate our search for an obvious crystal ball about what places to avoid. He found that cliffs that had lots of erosion in the past were eroding less now, and cliffs without a history of major erosion could erode a lot more. As a press release summarizing the study pointed out, “These are key findings, because models predicting future cliff retreat are often based on projecting the historical rates.”

In his research, Young has looked over a litany of major erosion events. He talks about them with the precision of a sports geek recalling box scores from baseball games played back in the days of radio. His vault includes the temple collapse in Encinitas and the recent hot spots up and down the San Diego coast, where parking lots and campgrounds and railroad tracks that might look at first like any other are beginning to crumble.

Young said we’ve manipulated our coastline so much it’s very hard to separate what we’ve done from the natural processes, in part because there isn’t good historical records that show exactly how cliffs used to look.

The California Coastal Records Project has detailed photos of the coast going back to the 1970s, but the images, taken from a helicopter, are far from perfect and 50 years isn’t a lot of time, geologically speaking. Lots of research is being done using modern radar imaging, which can show coastal geology down to the rock. But, of course, it only shows what the bluffs look like now, not how they used to be.

Last week’s deaths were far from the first. In 2008, a tourist from Nevada was killed when a bluff collapsed near Torrey Pines. A year later, rocks fell again in the same area near what’s called Bathtub Rock.

Just a few weeks ago, I was walking near that area of the beach, which is now open and a seemingly good site for selfies, which tourists were taking. But getting there from the parking lot on the north end of the beach, I noticed a large rock atop a cliff. It seemed to be half on the ground and half in the air, waiting to fall eventually.

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