By Dana Feldman

LOS ANGELES (Reuters) - Waves from a cyclone in the Pacific Ocean caused significant damage at picturesque Catalina Island in Southern California, demolishing piers, knocking boats from their stands and eroding a section of beach, officials said on Thursday.

Tropical Storm Marie, a former hurricane that is in the Pacific about 900 miles southwest of Los Angeles, has sent large waves crashing along the Southern California coast since Tuesday, and conditions will persist on Friday, National Weather Service officials said.

Waves as high as 20 feet have struck the southern side of Catalina Island, which is about 30 miles south of Long Beach, and was directly in the path of the giant waves, said Weather Service meteorologist Joe Sirard.

On the eastern side of the island, up to 10-foot waves washed over the seawall and badly damaged a boatyard at Pebbly Beach, said Ben Harvey, city manager of Avalon, the only incorporated municipality on the island.

"We saw a significant amount of activity here - boats coming ashore and landing on vehicles and resting against buildings," he said.

The surge caused flooding damage to businesses, scattered lumber, debris and large boulders across the area, and wiped out up to 6 inches of sand from an area popular with beachgoers.

Harvey estimated the losses for Avalon City at $3 million to $5 million.

The loss figure was "just for structural damage and doesn't include loss of business," he said. "We're a 100 percent tourist economy, so this is a significant impact to us."

Waves from Marie were the largest seen in Southern California since a pair of hurricanes swept through the Pacific within weeks of each other in 1997, the National Weather Service said.

Although cleanup had begun in some areas, a full damage assessment cannot be completed until the storm moves out of the area, said Andrew Veis, spokesman for Los Angeles County Supervisor Don Knabe.

In Ventura County at Point Mugu, the historic Cove House, which was built in the 1950s and later converted to a lifeguard station, was ravaged by breakers, said Craig Sap, superintendent for California State Parks Angeles District.

Surfers at the celebrity haven of Malibu reveled in the large waves again on Thursday, but city officials closed its pier after the surge damaged pilings.


(Reporting by Alex Dobuzinskis and Dana Feldman; Editing by Victoria Cavaliere and Peter Cooney)