Where’s all the sand in La Jolla? First of a two-part look at La Jolla beach erosion

A carpet of pebbles covers the sands of Tourmaline Surfing Park. The ocean washes the rocks at WindanSea. The waves dangerously approach Highway 101 at Torrey Pines.

La Jolla beaches present an erosion level that has surprised residents and visitors this spring. The La Jolla Light has received several letters from concerned beach-goers who want to know why their sandy, wide beaches have turned into narrow rocky corridors. We decided to look into it and shed light on the question: Should anyone do anything about beach erosion?Here’s what we discovered ...

Sand comes and goes with the seasons; that is the nature’s way. During the fall and winter sand is taken from the part of the beach where we walk and deposited deeper on the ocean’s floor. The next spring and summer brings that sand back to where it was.

During El Niño years, the sand retreat is expected to be greater than during a normal winter. Principal Regional Planner Robert Rundle, a sand expert at the San Diego Association of Governments (SANDAG), explained how this happens every few years.

“With El Niño we see a lot stronger storms so it exacerbates that natural occurrence,” he said. “However, not all of that sand will come back. If it surpasses the 44-foot depth level, the currents won’t take it back to the beach. So, most of the sand comes back, but there’s a part of it that gets lost every year.”

In a natural undeveloped environment, that sand would be replenished with sediment carried by rivers and bluff erosion. In the past century, however, in the development of Southern California, dams were created on the rivers and houses were built too close to cliffs that would otherwise erode onto the beaches, so those sand supplies are lost.

Can we do anything about it?

The cities of Encinitas and Solana Beach approved last October a 50-year plan to manage their coasts through beach nourishment that would cost $164.9 million.

Beach nourishment is an artificial, man-made substitute to the natural replenishment of sand that places it on a beach after being dredged from elsewhere. There are “opportunistic” beach nourishment programs that use sand that results from different development projects, for instance the construction of the trolley in Solana Beach.

The Encinitas and Solana Beach plans include a mix of opportunistic and non-opportunistic projects to maintain the sand level of their beaches in good condition. Marco Gonzalez is a long-time coastal conservation activist who was involved in this project from the beginning. “If we don’t replenish our beaches with sand, then the only option is to either build seawalls or to remove structures,” Gonzalez said.

A bit of history

The San Diego coastline has undergone two big beach nourishment programs in recent history. The first one, in 2001, placed 2.1 million cubic yards of sand in 12 receiver beaches, including Torrey Pines. At Torrey Pines, the beach fill consisted of 245,000 cubic yards of fine sand placed from April 6 to April 27.

The second beach nourishment program happened in 2011 and placed 1.5 million cubic yards of sand on eight beaches for $26 million. This time, Torrey Pines beach was not included.

La Jolla Shores has never been part of any nourishment programs, said Rundle. “We have never placed sand in La Jolla, that’s never been part of our program, primarily because of the near shore environment in La Jolla where there’s a lot of kelp and reef.”

Picture 1 shows the sand level of Torrey Pines before the first SANDAG regional sand program, and in Picture 2 the increase of walking area in the beach after the nourishment can be appreciated. Those are aerial pictures taken by SANDAG during their monitoring studies of the nourished beaches. Picture 3 shows the low levels of sand that the local beach currently presents after a high season of El Niño waves and storms.

Is Torrey Pinesrunning out of sand?

In terms of wave heights and weather conditions, the El Niño climate patterns of the years 2009-2010 and 2015-2016 were similar. However, the effects of the extreme erosion agent on West Coast beaches was very different from along the San Diego coast.

Scripps scientists have analyzed the changes in sand levels on four San Diego beaches throughout seven years and linked that information to weather patterns. Three of those beaches — Cardiff, Solana and Imperial – received a sand placement in 2012, and the fourth one — Torrey Pines — didn’t. They found that the nourished beaches were far less eroded than those that weren’t.

Scientists B. C. Ludka, T. Gallien, S.C. Crosby and Robert C. Guza wrote the paper “Mid-El Niño erosion at nourished and un-nourished Southern California Beaches,” which was accepted into the Geophysical Research Letters journal on April 22.

their research suggests, Torrey Pines’ sand level descended 13 meters (42 feet) during the 2009-2010 storms. This measurement reached a minimum of minus-15 meters (-49 feet) after the 2016 El Niño storms. Under similar conditions, nearby beaches that received sand, like Solana and Cardiff, lost 6 meters (19 feet) of sand surface in 2016, considerably less than they lost in 2010, which was 22 meters (72 feet) and 15 meters (49 feet) respectively.

Guza said he has concerns about the low levels of sand that Torrey Pines beach presents this year. “If you drive along Highway 101 you will see what I’m talking about; the beach is cut right through the highway (at Torrey Pines),” he said.

What happens with the sand?

Around 50 leopard sharks were found dead April 12 on the banks of the Tijuana River. A sand blockage at the mouth of the river prevented the animals from swimming into the ocean. Guza believes this event is related to the 2012 nourishment programs. “In Imperial Beach, there was so much sand that I think it contributed to clogging the mouth of the Tijuana River,” he explained.

Guza’s theory is that even if our perception tells us that nourishment sand is washed away from the beach, it doesn’t completely go away. Instead, the sand stays in the reach of currents before the 44-foot depth, where it can be naturally placed back on the beach.

The scientists also maintain that placing sand on our beaches lends protection to our coast against El Niño episodes. “In February 2016, Cardiff, Solana and Imperial Beach, nourished in Fall 2012, were wider than 2009-2010 by 10 meters (32.8 feet) or more. Torrey Pines, nourished in 2001 … was eroded slightly below 2009-2010 levels,” they wrote in their paper.

Not all the scientific community agrees with this notion. Gary Griggs is the Director of the Institute of Marine Sciences at UC Santa Cruz. His research is focused on the coastal zone, and he has published several papers about the quick disappearance of artificially nourished sand in Southern California beaches.

He studied how sand vanished from the Torrey Pines beach after the 2001 SANDAG nourishment. “A detailed study of the Torrey Pines State Beach fill project was carried out as part of the post-nourishment monitoring,” Griggs and Nicole Kinsman write in their report “Beach widths, cliff slopes, and artificial nourishment along the California Coast.”

“The fill was stable for approximately seven months of low wave energy conditions, but was removed from the subaerial beach (exposed at low tide) within a day when the first large waves of the winter arrived, suggesting that there may have been a significant sand deficit extending across the entire beach profile and offshore,” they conclude.

Although Griggs and Guza seem to disagree on sand nourishment, the truth is they’ve both found that placing sand on beaches helps having sandy beaches and seems to protect our shorelines from El Niño effects. The only point where they seem to disagree is on how long that sand stays in the system.

Is replenishment worth it?

Guza explained that to find out if sand nourishment projects are worthwhile, we should compare the costs with the benefits. “Nourishments cost money, they are not free; the sand is free, but you have to get it from miles away and that costs millions of dollars.”

▪: In part two of this report, La Jolla Light will analyze the costs and benefits of a beach nourishment plan, its effects on the ecosystem, and much more.

▪Got photos to share? If you’ve seen the effects of El Niño along our coast, please e-mail your pictures to mduran@lajollalight.com