If you live along or visit the west coast of California you have likely seen various types of structures designed to stop the coastline from eroding. Two common ways to decrease erosion are to place rip-rap (1– to 2–ton boulders boulders) along the cliff edges and to construct concrete sea walls. In recent decades, these methods of protecting or “armoring” the coast are so pervasive that people might not even notice them. I live near West Cliff Drive in Santa Cruz, California, and I am often amazed that people strolling along this beautiful section of the coast don’t even realize that rip-rap is not a natural feature.
Development and Storms
Much of the development along the California Coast, including Santa Cruz, took place between the mid-1940s and the mid-1970s—a three decades-long period of below-average rainfall and storm frequency. In the late 1970s the stable weather period began to change with large storms in 1977–78 and 1982–83. These storms led to increased studies of trends in ocean and atmospheric circulation.
These studies found that changes in atmospheric pressure, wind patterns, and ocean circulation in the equatorial Pacific create cycles known as the El Niño/La Niña Southern Oscillation (ENSO). El Niño conditions create more severe weather with above average rainfall and more frequent coastal storms. In contrast, La Niña conditions create mild weather with below normal rainfall and storm frequency. Seventy five percent of the storms that have been particularly damaging between 1910 and 1995 occurred during El Niño events.
The El Niño of 1982–83
The El Niño storms of 1982–83 did more damage than any winter since. That winter, eight major storms hit the California coast and were particularly damaging for several reasons. First, sea levels were already elevated by the warmer El Niño conditions; second, many of the storms hit at the peak in spring high tides (thus they scoured away more sand and reached higher and further onshore); and third, the swells came not from the northwest as is typical but from the west (where the waves struck the coast dead on with no energy loss from refraction) and southwest (directing energy to areas that are typically more sheltered). Thirty three ocean-front homes were destroyed and over 3,000 homes and businesses were damaged.
The Armoring of West Cliff
The first rip-rap on West Cliff Drive was installed in the mid-1960s. However, most of the armoring there today was installed in the 1980s and early 1990s, which was a period with several strong El Niño events.
Armoring also impacts coastal ecology by covering beach habitat used by birds and fish, algae, and invertebrates. For example, birds need protected rocks along the coast to roost and breed. Because armoring prevents the formation of new peninsulas, arches, and sea stacks in favor of a smooth armored coast, this habitat will get even more scarce.
The Coastal Commission
The California Coastal Commission was created by the voters of California in 1976 and regulates development along the coast. Under their regulations new armor is only allowed to protect existing structures that are threatened. New development must be set back far enough to avoid being threatened by erosion for its projected lifespan. However, these regulations are sometimes evaded due to ambiguous language and politics.
Adding sand to beaches, which can increase beach width and decrease erosion has been tried and considered as a long-term mitigation strategy. But the financial costs are huge and the effectiveness variable and often only short-term, especially in California where sand moves southward along the coast at high rates (a process known as littoral drift).
The Future of the Coast
Eighty six percent of California’s coast is eroding. A rising sea level and more severe and perhaps more frequent storms from human-induced climate change will only exacerbate coastal erosion. From the perspective of a homeowner on West Cliff Drive, or on any part of the California Coast, protection from wave erosion is important. However, it comes at a high cost. Millions of dollars of federal, state, and private money are spent every year on coastal armoring.
What do you think about the varying trade-offs to homeowners, the public, animals, and the environment? Should new development along the coast be allowed? Should existing structures be allowed to protect themselves indefinitely—and at whose cost? In some cases structures have been torn down or moved. The coastline is retreating landward, and this trend will continue and probably accelerate.
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This piece is part of the West Cliff Drive Tour. Download the free app with many tours of the Santa Cruz area and beyond.
- El Niño Southern Oscillation: Cold and Warm Episodes by Season. US National Weather Service Climate Prediction Center. National Oceanic and Atmospheric Administration Website.
- "The Impacts of Coastal Protection Structures in California’s Monterey Bay National Marine Sanctuary," by Rebecca Stamski. Marine Sanctuaries Conservation Series, MSD-05-3, 2005. US Department of Commerce, National Oceanic and Atmospheric Administration, Marine
- Living with the Changing California Coast, by Gary B. Griggs, Kiki Patsch, and Lauret E. Savoy. University of California Press, 2005.