OREGON STATE UNIVERSITY

El Nino could tear at West Coast shorelines

11/12/1997

CORVALLIS, Ore. - West Coast beaches could lose thousands of yards of shoreline, and homes and bays could be endangered as El Nino settles in for the winter, according to an Oregon State University researcher who monitored damage to Oregon coastlines more than a decade ago.

No one knows if this season's erosion will match the magnitude of the 1982-83 El Nino, when celebrity homes were dumped into the sea at Malibu, Calif., and pieces of the Oregon Coast were ripped away by massive waves, said Paul Komar, an OSU professor of oceanic and atmospheric sciences.

But there is the potential for a serious coastal menace, Komar said.

"We now understand that El Ninos affect far more than the fisheries of Peru, they can also have major impacts on erosion on the Northwest Coast. Now, when we hear news reports that another El Nino may be developing, we have a justifiable feeling of apprehension," said Komar, who is the author of several books on erosion and serves as editor of the journal Shore and Beach, which focuses on the science and management of coastal erosion.

 

"The 1982-83 El Nino event caused a range of unusual conditions on the coast," Komar said. "There was a substantial rise in overall sea level for up to six months, a change in the direction of some storm patterns and three unusually large, intense storms with very high waves up to a 23-foot average height."

If conditions this winter mimic those in place during the 1982-83 El Nino, damage along West Coast beaches could be brutal, he said.

During the 1982-83 El Nino, the area sustaining the greatest erosion was Alsea Spit at the Central Oregon Coast town of Waldport. But few areas of the coast were spared, Komar said.

Komar stresses that no one know how the factors will fall into place as winter progresses. Increased sea levels spawned by El Nino don't cause significant erosion - the key is the combination of factors, he said. And erosion isn't the only problem. Some areas could have too much sand.

In 1983, north of Newport's Yaquina Head, the beach eroded to bedrock, while south of the headland, so much sand was deposited by the shift in currents that a large dune field was formed.

Generally, El Ninos cause a northward movement of sand along the coast, resulting in sand erosion on the south ends of Oregon pocket beaches and accumulation of sand at the north ends. In 1982-83, this erosion pattern stripped away sand buffers along cliffs just north of headlands, exposing them to the direct force of storm waves and causing large pockets of erosion.

El Nino was first named about 200 years ago by South American fishermen who noticed that in some years cold water currents along the coast were being replaced by warmer tropical waters. The event usually begins to intensify near the end of December, so fishermen associated it with the story of Christ and named it El Nino - Spanish for The Child. The peak months of El Nino usually last through February, but the effects of the phenomena can be felt for several years after the event, Komar said.

During normal years, trade winds blow westward from the coast of South America toward Asia, causing an elevated sea level along the Asian coast. During El Nino periods, these winds are disrupted and the water surges back across the Pacific toward the Americas, Komar said.

"You can duplicate the effect of El Nino along the West Coast by blowing across a cup of coffee. The surface of the coffee becomes highest on the side away from you. If you stop blowing, the coffee surges back and runs up the side of your cup. This is similar to what happens when the tradewinds stop blowing during El Nino. It produces an eastward flow of warm water along the equator toward Peru."

When this flow reaches the South American coast, it splits, with water moving both north and south. During the 1982-83 El Nino, this flow pushed water higher along the U.S. West Coast, until the maximum increase of about 24 inches was reached in February, 1983.