Extremely high "king tides" surged ashore along the Sonoma County coast Thursday, filling Bodega Bay to the brim and bringing crashing surf to the base of the bluffs at Salmon Creek.

"It is quite a sight. I had to go out and look at it," said Noah Wagner, supervisor of Spud Point Marina at Bodega Bay.

The tide peaked at 7 feet, the highest tide of the year, at the entrance to Bodega Bay shortly before 9:56 a.m.

In Petaluma, high tide reached 8.2 feet at the D Street Bridge on the Petaluma River at 12:45 p.m.

The extreme tides began Wednesday and continue today, although the tides will be slightly smaller than Thursday's.

King tides, which occur several times a year, are caused when the Earth, moon and sun align in a way that increases the gravitational pull on the ocean, raising water levels several feet above normal high tides.

"King tides have been around. They are mostly in the winter and anyone who lives close to the water is used to seeing the water rise," said Deb Self, executive director of San Francisco Baykeeper, a conservation group.

Luckily, the weather this week has been mild and the tides have caused no harm in Sonoma County. But in Marin County, the tide swamped a commuter parking lot in Marin City and seeped into dozens of cars. In Southern California, seawater flooded a low-lying section of Pacific Coast Highway and side streets near Huntington Beach.

Coupled with wind, rain and rough seas, king tides can cause flooding and damage.

"If there were any waves, it'd be coming right into the marina and wreaking havoc," said Chris Starbird of Petaluma, who was tending his oyster nursery at the Spud Point Marina on Thursday.

"When we have a very high tide and south winds, it will blow water and debris across the road at the other end of the bay," said salmon fisherman Mat Keller of Occidental. "It would be quite a mess."

Bodega Bay was dead calm on Thursday, but so full of water that it was within inches of inundating the marina's breakwater.

As it was, water lapped over the concrete fishing pier any time a passing boat created a small wake.

Directly south of the marina, Gaffney Point Salt Marsh was submerged. Only an outer island of spike grass and pickleweed and the very tops of salt marsh bull rushes poked through the water nearer to shore.

"It almost looks like there isn't a salt marsh here at all," said Jackie Sones, research coordinator for the Bodega Marine Reserve.

To the north, at Salmon Creek State Beach, the ocean overtook a beach that is usually 200 feet wide, sending waves crashing directly onto the bluffs.

At the small community of Salmon Creek, the tide was pushing the creek level nervously close, but the water never reached Bean Avenue and homes that line the narrow street.

King tides happen about four times a year, usually in November, December, January and February. Conservationists are using this week's king tides as a preview of the future. They say the surge of water reveals what will happen to the coast, bays and nearby roads and buildings because of climate change.

The National Academy of Sciences predicts the sea level will rise 5 feet by 2100 as the earth warms and polar ice caps melt.

"We need to raise enough public awareness so there is support for planning, so cities can adapt to the sea level rise," Self said.

"We know what the future will bring. We know we will have 5 feet of bay level rise by the turn of the century. This is about educating people to see what we have to adapt to now," she said.

Ruth Tonascia of Santa Rosa was at Bodega Bay to take pictures for the California King Tides Initiative, which asked people to submit photos from different areas to document the high tide throughout the state.

The initiative was formed by the California Coastal Commission, California Coastkeeper Alliance, Gulf of the Farallones National Marine Sanctuaries, San Francisco Bay National Estuarine Research Reserve, Thank You Ocean and Tijuana River National Estuarine Research Reserve.

This story includes information from the Associated Press.

You can reach Staff Writer Bob Norberg at 521-5206 or bob.norberg@pressdemocrat.com.