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Widespread erosion associated with energetic waves of the strong 2015–2016 El Niño on the U.S. West Coast has been reported widely. However, Southern California was often sheltered from the northerly approach direction of the offshore waves. The few large swells that reached Southern California were not synchronous with the highest tides. Although west coast‐wide tidal anomalies were relatively large in 2015–2016, in Southern California, total water levels (sum of tides, anomalies, and wave superelevation) were lower than during the 1997–1998 Niño, and comparable to the 2009–2010 Niño. Airborne lidar surveys spanning 300 km of Southern California coast show the beach response varied from considerable erosion to accretion. On average, the shoreline moved landward 10 m, similar to the 2009–2010 El Niño. Some San Diego county beaches were narrower in the 1997–1998 El Niño than in 2015–2016, consistent with the higher erosion potential in 1997–1998. Beach retreat exceeded 80 m at a few locations. However, 27% of the shoreline accreted, often in pocket beaches, or near jetties. While adjacent beaches eroded, estuary mouths accreted slightly, and several estuaries remained or became closed during the study period. Only 12% of cliffs eroded (mostly at the base), and the average cliff face retreat was markedly less than historical values. Only two cliff‐top areas retreated significantly. Although some areas experienced significant change, the potential for coastal erosion and damage in Southern California was reduced compared to the 1997–1998 El Niño, because of low rainfall, a northerly swell approach, and relatively limited total high‐water levels. Key Points: Southern California beach response to the 2015–2016 El Niño varied widely, from considerable erosion to accretionSome coastal erosion and damage were limited by the timing of high tides and large waves, northerly swell direction, and low rainfallEstuary mouths on average accreted, while their adjacent beaches eroded. Many estuaries remained or became closed during the study [ABSTRACT FROM AUTHOR]

Seacliff changes evaluated using both terrestrial and airborne lidar are compared along a 400 m length of coast in Del Mar, California. The many large slides occurring during the rainy, six-month study period (September 2004 to April 2005) were captured by both systems, and the alongshore variation of cliff face volume changes estimated with the airborne and terrestrial systems are strongly correlated (r² = 0.95). However, relatively small changes in the cliff face are reliably detected only with the more accurate terrestrial lidar, and the total eroded volume estimated with the terrestrial system was 30 percent larger than the corresponding airborne estimate. Although relatively small cliff changes are not detected, the airborne system can rapidly survey long cliff lengths and provides coverage on the cliff top and beach at the cliff base. [ABSTRACT FROM AUTHOR]