Storm waves eroded the dunes from beneath homes in Pajaro Dunes, Calif., on Monterey Bay, during the powerful 1982-83 El Nino. Gary GriggsCalifornia’s coastal bluffs and beaches look rugged, but they can be surprisingly fragile in the face of a powerful El Niño.The state saw that in 1982-83, when storms amid one of the most destructive El Niño winters in California history battered the coastline with powerful waves and torrential rain, leaving hundreds of millions of dollars in damage in its wake. The storms coincided with elevated sea levels, high astronomical tides and very large waves delivered by repeated storms.Extreme waves that winter destroyed one-third of the Santa Monica Pier and tore off large sections of the Huntington Beach Pier and the Paradise Cove Pier, while also damaging the Seal Beach, San Clemente and Malibu piers. Numerous seawalls, decks and stairways were torn apart, and 33 oceanfront homes were destroyed. Massive waves also stripped millions of cubic yards of sand from Southern California beaches, and sections of the Pacific Coast Highway suffered severe flooding, mudslides and washouts. A powerful El Niño in 1978 was a wake-up call for coastal residents who had built homes on the beaches, sand dunes and fragile cliffs. These homes were on Pot Belly Beach, near Santa Cruz, Calif. Gary Griggs Along the central coast, waves and high-tide flooding eroded bluffs. In Pacifica, just outside San Francisco, the edge of a sandy cliff lost over 65 feet as it failed, collapsing onto the beach and forcing the relocation of a two-story building and removal of an entire row of mobile homes. This area of high but weak bluffs continued to erode over the subsequent decades, forcing the demolition of bluff-top homes and apartments.The El Niño now building in 2026-27 is forecast to be even stronger, and coastal homes are already seeing damage. I have studied coastal geology and oceanography in California for nearly six decades. With the conditions expected this year, coastal flooding, coastal erosion and landslides are likely, and more dramatic cliff collapses wouldn’t be a surprise, though every El Niño is different.What is El Niño and why is it so destructive?El Niño is one end of a climate pattern that swings from warm to cold every few years and can change weather patterns around the world. Normally dry areas can experience flooding rains, and wet areas can suffer droughts. The U.S. Pacific Coast in particular can take a beating from powerful atmospheric river storms with heavy downpours.El Niños begin with a shift in wind patterns, which normally push warm waters from east to west along the equator. For reasons still not fully understood, the trade winds die and the warm pool of water in the western Pacific begins to flow back toward the coast of South America. What is El Niño? Met Office. Part of this warm mass moves north toward the coast of California as a pulse or bulge, known as a Kelvin wave, and it begins to have far-ranging impacts.Seawater expands as it warms, which raises sea level along the Pacific Coast for weeks during these periodic events. While all El Niños are not created equal, during the very large 1982-83 event, sea levels were elevated above predicted high tides by about a foot in San Diego to nearly 2 feet in San Francisco.These higher sea levels can reach higher elevations and last longer. The 1982-83 El Nino destroyed timber bulkheads and seawalls and damaged several piers along the California coast. Gary Griggs The elevated sea levels also allow storm waves to break closer to the shoreline, eroding beaches and bluffs, leading to damage and destruction of both private oceanfront development and public infrastructure, including streets and highways, bridges and piers, and parks and recreational facilities.Why California is vulnerableMuch of California’s coastal and shoreline development took place from the late 1940s to the late 1970s when the state’s population exploded.Homes were built on beaches, bluffs and dunes during a period when the coastal storm climate was generally mild and there were no real concerns with coastal hazards and future sea-level rise. The piers beneath these buildings on the cliff at Capitola, Calif., had little left to stand on after erosion from fierce El Niño-fueled storms. Gary Griggs This changed quickly in 1978 when the first strong El Niño in recent memory arrived, raising alarm about the hazards ocean development was exposed to.The extreme 1982-83 El Niño that followed a few years later caused about US$328 million (in 2025 dollars) in damage to oceanfront property, $87 million in losses to recreational facilities such as piers, parking lots and access stairs, and $66 million in damage to large engineering structures such as breakwaters and jetties designed to protect harbors from storm waves.At least in the short term, the 1982-83 El Niño winter changed popular perceptions of the stability or security of oceanfront homes and other shoreline development. Building restrictions were tightened, insurance rates rose, and many requests for new seawall permits were submitted.But then it was back to business as usual, as new arrivals to the coast outbid each other for the same oceanfront homes damaged a few years before. Gary Griggs talks about erosion risks in the Santa Cruz area at the Seymour Marine Discovery Center. Increased coastal armoring, such as seawalls and rock revetments, helped limit erosion during other very large El Niños that followed, in 1997-98 and 2015-16, along with lucky timing that large waves arrived at low points in the monthly tidal cycle, leading to significantly less property damage than in 1982-83.The coast was not so fortunate in winter 2022-23, when high seas and waves alone caused an estimated $4.7 billion in economic losses along California’s coast. The simultaneous occurrence of large storm waves, high tides and elevated sea levels were almost identical to the El Niño conditions in early 1983, 40 years earlier. The state’s latest climate assessment, released Oct. 19, 2026, warns of more intense storms and increased erosion as temperatures increase and sea level continues to rise.The El Niño of 2026-27What will California see in 2026-27?The southern end of the state is already suffering wave damage from an exceptionally busy Pacific hurricane season, also fueled by El Niño. Swells have stripped away beaches and destroyed homes near San Diego. The state’s storm season, when powerful atmospheric rivers bring downpours, typically begins in October or November and runs through early spring.The magnitude of the emerging 2026-27 El Niño, likely to be one of the strongest on record, is making clear that coastal communities need to adapt now to a very different future. Pacific Ocean waves generated by Hurricane Marie crash over a seawall protecting homes in Long Beach, Calif., on Sept. 7, 2026. El Nino’s warm water was already fueling powerful storms in the Pacific. Mario Tama/Getty Images How each coastal neighborhood, city and county responds will vary depending upon their local conditions and vulnerability to coastal erosion and flooding.While many communities are stockpiling sandbags, clearing culverts and preparing evacuation plans, there are limits on what they can do to stop erosion. Building seawalls and rock revetments can provide some protection if well designed, but they can also create new problems, including leading to the loss of beaches over time as sea levels continue to rise. Putting more sand on beaches is costly and very short-lived.Extensive shoreline development, eroding bluffs, aging infrastructure and increasing exposure to extreme weather are placing growing pressure on coastal communities and shorelines around the world. Some will eventually face the difficult transition from continued shoreline protection to retreating from the coast – either planned retreat or following repeated damage. There is little that any developed coastal area can do at this point to minimize the impacts of the El Niño underway. What they can do is prepare to manage the risks and try to adapt to the changing future.Gary Griggs does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.