Beaches along Washington’s coast eroded at a record pace during the 2015-16 El Niño season.
That’s the conclusion of a study released Tuesday in the journal Nature Communications.
U.S. Geological Survey scientists and their colleagues say the most recent El Niño climate event was one of the most powerful in the past 145 years.
“The winter wave energy equaled or exceeded measured historical maximums along the U.S. West Coast, corresponding to extreme beach erosion across the region,” said survey geologist Patrick Barnard.
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El Niño is the term used when ocean temperatures are higher than normal.
USGS scientists and their colleagues investigated 29 beaches along the West Coast, including three in Washington: North Beach, Grayland Plains and Long Beach.
The researchers found that winter beach erosion was 76 percent above normal, the highest ever recorded. Washington saw a two-fold increase in erosion over the 2014-15 season.
California got the worst of it, with most of its beaches eroded beyond historical extremes.
The Pacific Ocean has just finished a La Niña season, when ocean temperatures fall below average.
While the 2015-16 El Niño pounded the coast with waves, it brought little rain to drought-starved California. This winter made up for that with record-breaking rains and snow.
That might mean good news for beaches. Rivers bring sediment into the ocean which, in turn, replenish beaches that experience normal winter erosion.
Although Washington beaches did not see the extreme erosion that California beaches did, they had significant retreat, said study co-author and Oregon State University coastal hazards expert Peter Ruggiero.
“We’re not completely recovered yet, and it may take years for some beaches to build back up,” Ruggiero said. “After the 1997-98 El Niño, it took some beaches a decade to recover.”
The authors of the study made 3D surface maps and cross-shore profiles of the 29 beaches using aerial lidar (light detection and ranging), GPS topographic surveys and direct measurements of sand levels.
They combined the information with wave and water-level data collected at the beaches from 1997 to 2016.