Decade’s Highest Tide May Cause Coastal Flooding

High tides caused minor highway flooding Monday morning at Sunset Beach in Orange County and worried coastline property owners throughout the Southland--but that was only a taste of what may be in store on New Year’s Eve, when the highest California tide of the last decade is expected.

Monday morning’s tide was 7.1 feet along Los Angeles, Orange and San Diego counties’ coastlines, pushing 3 to 4 inches of water from Huntington Harbour into the northbound lanes of Pacific Coast Highway at Sunset Beach.

Alternate Routes

The California Highway Patrol, which blocked off the lane into Huntington Beach, plans to close part of the highway again this morning between 7:30 a.m. and about 10 a.m., when a 7.2-foot tide is due, and on Wednesday, when it will be 7 feet. Public affairs officer Kevin Dougherty in Westminster said the CHP suggests that motorists use alternate routes. There was minor street flooding Monday morning on the ocean side of Pacific Coast Highway, but no homes were affected.

In Newport Beach, several streets on the Balboa Peninsula were also flooded. But there were no reports of property damage, according to city engineer Don Webb, who called the watery streets a routine occurrence. “When tides are above a certain level, sometimes we do get water in the streets,” he said.

There were also reports of water on Pacific Coast Highway at Malibu, but a sheriff’s station deputy said a patrol officer was unable to find it.

In San Diego, Monday morning’s 7.1-foot tide carried surf to the seawall at Mission Beach. Lifeguards moved trash cans onto the boardwalk in anticipation of a 7.8-foot tide at 8:48 a.m. today.

The increased tides this week, at the end of December and at the end of January are the result of two celestial events known as perigee and syzygy, which were first recognized by Fergus J. Wood, a retired National Ocean Survey meteorologist. The survey is a branch of the National Oceanic and Atmospheric Administration.

Perigee is the point at which the moon in its irregular orbit is closest to Earth, a position that strengthens the gravitational pull that causes tides.

Tidal Surges

Syzygy refers to the near-alignment of the sun, moon and Earth, which also causes an increase in tides.

When perigee and syzygy occur close together, their effects are combined and record tidal surges can result.

The Dec. 31 tide will average about 7.5 feet along the state’s coastline, according to the National Ocean Survey.

That tide may not cause any significant flooding on its own, even in low-lying coastal areas, unless an offshore storm occurs at the same time, in which case flooding could be severe, experts caution.

On Dec. 31, perigee and syzygy will be four hours apart. High tide in Los Angeles will be 7.3 feet at 8:30 a.m. Normal high tides vary between four and five feet.

In San Diego, high tide on New Year’s Eve will be 7.8 feet; in San Francisco it will be 7.4 feet.

On Jan. 29, high tide in Los Angeles will be 7.1 feet.

Tides should not be confused with sea level. Tides are the up-and-down motion of waves caused by the gravitational interaction between the Earth, moon and sun. They are “absolutely predictable,” according to oceanographer Reinhard E. Flick of the Scripps Institution of Oceanography. Sea levels are affected by wind, rain and other meteorological factors.

In January, 1983, a high tide combined with an offshore storm produced the worst flooding in Southern California in 20 years, resulting in damage estimated at more than $3 million.

Sea level at the time was about nine inches above normal as a result of El Nino, a major warming of water and winds in the tropical Pacific, and that further magnified the effects of the high tide, according to Wood.

15-Foot Waves

On Jan. 26, 1983, the storm dumped up to five inches of rain at many sites between the Oregon border and San Diego and pounded oceanfront communities with waves as high as 15 feet. Santa Monica’s municipal pier was heavily damaged, as were the Seal Beach pier in Orange County and the Crystal Pier in San Diego.

In addition, streets and homes were flooded in Malibu, Venice, Playa del Rey and the King Harbor area of Redondo Beach. About 750 residents were also evacuated from homes in Seal Beach and Sunset Beach because of flooding.

In March, 1962, perigee and syzygy were only 31 minutes apart, according to Wood. A major storm occurred in the Atlantic Ocean at the same time, producing more than $500 million in coastal damage from South Carolina to Maine and killing 40 people.

People who live in the areas affected by the 1983 storm “should stay alert to the weather predictions,” Wood said. “If there is a strong onshore wind or major storms offshore, there is a good chance that flooding could occur again.”

The next time such high tides will be caused by perigee and syzygy will be Oct. 14, 1989.