Californians living near the coast expect the ocean to occasionally rise high enough that it briefly threatens to swamp docks and sidewalks and flood into a few patios and storefronts.

It’s a twice-a-year condition known as king tide, and it’s hitting the West Coast today.

In Long Beach 6,000 people live in vulnerable areas over 1.3 square miles, and $1.3 billion in property is threatened, according to Climate Central. Each year Long Beach workers fortify the beaches along the peninsula, adding sand to widen the beach and berms to act as a buffer against high tides and storms.

The city has also partnered with the Aquarium of the Pacific, Cal State Long Beach UCLA, the Port of Long Beach and other agencies to find the areas most sensitive to sea level rise.

Scientists who study the phenomenon look at king tide and see something else, too; a glimpse of the future. What’s currently an extreme event prompted by the pull of the moon could become a routine event prompted by global warming, possibly within a generation.

“This could be the norm in 20 to 30 years,” said Lesley Ewing, a senior coastal engineer with the California Coastal Commission, referring to today’s king tide, which is expected to top 7 feet, nearly twice as high as a typical high tide.

“It’s not going to be 10 days a year, for a couple of hours,” Ewing added. “It’s going to be 50, 60 days a year. (And) rather than a two-hour window of high waters… it will be substantially longer.”

King tides coupled with the effects of storm surges, wind and high surf can damage virtually every type of coastal property, from sand-front mansions to public walkways to industrial equipment needed to run modern ports in places like Long Beach.

And that’s damage done to a coastline largely designed to handle the king tides, and ocean levels, of the mid-20th century. Conditions are changing rapidly.

“We’ve designed our coastal infrastructure and our roads for the highest tides we expect to occur without sea level rise,“ said Peter Gleick, the founder and chief scientist of the Pacific Institute, a non-profit research center based in Oakland.

“We now live at a period of history when sea level rise is going up.”

The king tides hitting this week aren’t expected to do much damage locally. Typically, even a big king tide needs some sort of accelerant – such as a severe storm or huge waves – to cause damage. Those conditions aren’t in place this week.

But cities and residents along California coast won’t always have such luck.

“As the sea level gets (higher), the damages that occur during high tides will get worse,” Gleick said. “That’s our inevitable future now.”

The sea level in California already has risen about eight inches over the past century. By some estimates, the sea level could rise by about three feet by 2100.

About a half-million people California residents currently live in areas that could flood if sea levels rise by 43 inches. Critical infrastructure, including roads, hospitals, schools and power plants, also are at risk. More than 26,000 acres of California’s coast could erode and $100 billion in property could be destroyed or abandoned, according to a 2009 report funded by several state agencies and created by the Pacific Institute.

Southern California is less at risk than cities in the Bay Area, where many miles of bay-front property lie below the projected flood areas, the report noted.

Of the five California cities with the greatest number of people living in potential flood areas, two are in Southern California: Long Beach and San Diego. The state’s most at-risk cities are Stockton, followed by Long Beach, San Jose, San Diego and San Francisco, according to an analysis from the non-profit Climate Central.

Other communities in Orange County also are at risk, according to the Climate Central data – Sunset Beach, Seal Beach, Huntington Beach and even non-coastal Costa Mesa.

Gleick sees two options for coastal areas – “protection or abandonment.“

“We will build sea walls where you’re protecting something really really valuable, like a new power plant, something that’s worth spending the enormous amount of money that sea walls cost,” Gleick said.

“The second option is retreat. We will have to abandon things along the coast that aren’t worth saving.”

He added that smaller changes, like creating climate insurance and limiting development along the coast, could lessen the impact on the people who live there as the sea level gradually climbs.

Many cities have started assessing how sensitive they are to rising sea levels, and a 2013 state law requires cities to have a plan on how to handle rising sea levels by 2019.

“There are always plans in California to build more. A lot of coastal development is still happening as though sea level rise as not going up.

“We have to start integrating sea level rise into our plans.”