A statewide study of coastal erosion shows that cliffs on the Central Coast have retreated on average nearly 57 feet over the past 70 years.
The study by the U.S. Geological Survey is the first comprehensive assessment of historical beach erosion in the state using data going back to 1933. It shows that the rate of local cliff retreat is nearly identical to the statewide average.
Coastal cliff erosion is a chronic problem in the state, said Cheryl Hapke, lead author of the report. It results in the loss of land and threatens blufftop homes and other private and community property.
“Besides being popular tourist and recreation locales, the coastal cliff environments of California constitute some of the most valuable real estate in the country,” the report concluded.
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The most severe erosion in the county occurred along a remote section of the Harmony Coast two and a half miles north of Cayucos State Beach, where the cliff retreated 172 feet over 70 years.
But the areas of the county where erosion poses the greatest danger to homes are areas along Cayucos State Beach, Morro Strand State Beach and Pismo Beach.
“Numerous seawalls and revetments exist along this stretch of coast, especially in more heavily developed areas,” the report states. “These structures built in response to cliff erosion threatening private homes and/or community infrastructure act to reduce the rate of cliff retreat.”
Coastal cliffs crumble as a result of a combination of wave erosion and water seepage from rain or irrigation. Promontories or points are also sites of high coastal erosion, including Point San Luis, Point Sal and Point Conception.
Erosion is worse during El Niño weather years, which are characterized by more intense storms and bigger waves. Earthquakes and landslides can also cause major erosion.
A landslide caused the greatest amount of erosion recorded in the study. A cliff near Cape Vizcaino in Mendocino County retreated 732 feet.
The Big Rock Mesa landslide near Santa Monica caused a cliff to erode nearly 378 feet. That was the worst amount of shoreline retreat recorded in Southern California during the 70 years covered by the study.