The 2015/16 El Nino event drove unprecedented levels of erosion along much of the west coast of the United States, making it one of the most powerful El Nino events of the past 145 years, according to a study published in Nature Communications. The authors caution that this extreme event may disrupt the equilibrium of US West Coast beaches for many years to come.

El Nino events are associated with increased storminess, higher wave energy and severe coastal erosion, particularly along the US West Coast. Despite warnings that the frequency of such climate extremes is likely to increase in the coming years, quantitative records are few and far between and provide no benchmark against which to prepare for future events.

Patrick Barnard and colleagues analyse wave conditions, water levels and coastal response of 29 beaches along the California, Oregon and Washington coasts during the 2015/16 El Nino event. The authors show that elevated sea levels and winter wave energies that were twice as high as normal resulted in coastal erosion 76% above normal winter shoreline retreat. The majority of beaches in California, where coastal sediment supply has been limited by a multi-year drought, experienced the greatest retreat since records of coastal elevation changes began 20 years ago.

The authors hope the findings will aid the short and long-term planning of coastal defences for the communities that occupy this stretch of coastline.