When this home, and the ones beside it, were originally designed and built, sand buried the entire foundation up to the bottom of the house, and the stairs led right onto the beach. Today, much of the sand is gone, the foundations of the homes are fully exposed and the stairs now lead to an eight-foot drop down to what is at times ocean water instead of beach.
Back in the 70’s, Broad Beach in Malibu used to be about 100-150 feet wide. Since then, the 1.1-mile oceanfront – lined with homes of the rich and famous – has become eroded by winter storms and high tides. When my friend, Devon Low, and I went there this past April, it seemed like it was ready for a name change – maybe something like Slim Sand.
Cliffs and bluffs, the dominant feature of the west coast, have been slowly retreating for thousands of years. Their rate of erosion depends on what they are made of as well as external forces. Cliff and bluff retreat happens periodically and suddenly from a variety of forces. Large blocks fail under heavy rainfall, large waves, or earthquakes. In steep, mountainous areas, failure is often through large landslides or rock falls, usually driven by excess or prolonged rainfall during the winter months. One example is the slide that occurred in November of 2012 when a 600-foot section of Paseo Del Mar in San Pedro below the White Point Nature Preserve suddenly dropped down the cliffside. It was the most damaging landslide on the Palos Verdes Peninsula since the 17th and 18th holes fell to the beach in 1999 from what’s now Trump National Golf Club.
A rising sea level would cause waves to break closer to the coastline and reach the bases of cliffs or bluffs more frequently, thereby increasing the rate of cliff retreat. According to one recent study, a 40” sea-level rise would accelerate erosion rates for southern California by 20 percent. The California Coastal Commission states that for gently sloping beaches, the general rule of thumb is that 50 to 100 feet of beach width is lost for every foot of sea-level rise.
Cliff and bluff erosion is not reversible. The most common response has been to armor the cliff base with rock revetments or seawalls. Ten percent (110 miles) of the California coastline is armored, including 33 percent of the coastline of the four most developed southern California counties: Ventura, Los Angeles, Orange, and San Diego. Despite this protection, coastal storm damage has increased over the past several decades because of intense development and several severe El Niño events. In addition, armored coastline ultimately reduces beach size.
“An armored coast blocks the natural sediment transport from the shore and in California we get a lot of sand on our beaches from creeks,” said Dana Murray, Heal the Bay’s Marine and Coastal Scientist. Thus, beaches cannot migrate landward, and continued flooding of the seaward beach results in a reduction in beach width, and its eventual loss entirely.
This also spells trouble for California grunions, which migrate to Pacific beaches, mostly from Punta Abreojos Mexico, to Santa Barbara, California every spring and summer. “The walls can diminish or even eliminate grunion spawning grounds,” said Melissa Studer, Project Director of the Grunion Greeter Project.
“Waves hit the wall and scour the sand out because they don’t have any where else to go, and as they keep hitting the wall, they bring all the sand back out,” Murray said. “So the beach gets eroded more and more. A rock revetment just makes the problem worse. Beach resident may stop it from going further, but in front of it, they’re losing the beach.”
Broad Beach residents want to restore their beach to its original width, and taxed themselves to foot a $20 million plan to borrow 600,000 cubic yards of sand. But these days they’re having trouble finding suppliers. Manhattan Beach has denied them sand from South Bay, so proponents of the privately-funded Broad Beach project are hoping to dredge sand off Dockweiler Beach. However, the Los Angeles County Department of Beaches and Harbors has objected, saying that the Broad Beach project would deplete reserves that might be needed later to replenish other public beaches eroded by rising sea levels.
If sea level increases substantially and wave heights continue to increase, over-topping will become more frequent. “Broad Beach’s rock wall is not supposed to last,” Murray said. “Even in their reports, they say they’ll last no longer than 5 or 10 years anyway because the rocks fall apart.”
In July, Kurt Russell and Goldie Hawn sold their Broad Beach home after two years of trying. Original sticker price: $14.749 million. Final sale price: $9.5 million. A sign of the times.
Originally published in Catalina Marine Society’s OceanBights, p. 12
California Coastal Commission, Climate Change Impacts on Coastal Erosion and Loss of Sandy Beaches
Tony Barboza, 600-foot section of road quietly slips into ocean
Martha Groves, On Broad Beach, slim progress on restoring sand
Melissa Studer, Fish “Walks” on Beach to Spawn
D. Devon Low