Climate change will put coastal areas from Sydney to California at increased risk from erosion and flooding, independent of sea-level rise, a new study suggests.

The research, published today in Nature Geoscience, is the first to link a pattern of beach erosion around the Pacific with the El Nino-Southern Oscillation (ENSO) climate cycle.

“Most people, when they talk about climate change and the coast, just talk about sea level,” said co-author marine scientist, Professor Andrew Short from the University of Sydney.

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“But whether sea level rises or not, we will still be getting shoreline changes taking place because of intensified cycles of El Nino and La Nina.”

Storms generate waves and a temporary increase in the sea level, known as a storm surge, due to strong onshore winds and low atmospheric pressure.

The more intense a storm, the bigger the waves and the bigger the storm surge, and together these can have a devastating effect.

Professor Short said recent evidence has suggested that the ENSO climate cycle will intensify with climate change, bringing more extreme El Nino and La Nina events, which will bring more stronger storms to the Pacific.

Sandbags line the shore as erosion threatens a beach in Kingscliff, NSW. Photo: ABC/Andrew Short

Western Pacific ‘would suffer inundation’

In a study designed to look at the impact of climate cycles, Professor Short and his colleagues found ENSO most strongly correlated with beach erosion.

They analysed records on wave conditions and shoreline position from 48 beaches around the Pacific including Australia, New Zealand, Hawaii, North America and Japan.

The data, collected between 1979 and 2012, revealed a pattern of change that matched the ENSO cycle.

The pattern was “synchronised, but out of phase”, Professor Short said.

Beaches in the western Pacific, including Australia, would suffer inundation and erosion during a La Nina phase.

At the very same time, beaches in the eastern Pacific, including North America, would experience a relatively calm period, during which they could at least partially recover.

“One side erodes while the other builds up,” Professor Short said.

“Anecdotally we’ve known things are different on either side of the Pacific, but no-one has ever done any study to verify this.”

The erosion hotspots include Kingscliff, Byron Bay, and Jimmy’s Beach in the state’s north, Stockton Beach near Newcastle, Collaroy in Sydney and Surfside near Bateman’s Bay in the state’s south.