Near-record or record-high sea levels are expected to bring multiple days of flooding along the Southern California coast this week, with the inundation beginning as soon as Monday morning when high tide rolls in.
Officials in Newport Beach and Long Beach have been scrambling to prepare as crews move sand to shore up beaches, install sandbags and otherwise work to protect areas, such as the Balboa Peninsula and the Long Beach Peninsula, hammered in recent month. Officials urged residents of flood-prone areas “to take precautions now,” including moving cars to higher ground and protecting property with sandbags.
Seawater levels could reach near-record or record heights across Southern California, the National Weather Service warned. The highest high tides are expected on Monday, Tuesday and Wednesday mornings.
Areas at highest risk of coastal flooding this week are Orange and San Diego counties, where the National Weather Service has issued a coastal flood warning that will last through Thursday afternoon.
“Significant coastal flooding expected,” the weather service said. “Low-lying property including homes, businesses, and some critical infrastructure will be inundated. Some shoreline erosion will occur in the morning hours.”
Farther north, in Los Angeles, Ventura, Santa Barbara and San Luis Obispo counties, a coastal flood advisory was issued, and “isolated damage of structures due to seawater inundation is possible to the most vulnerable areas.”
A rare combination of threats has brought damaging swells to Southern California’s coastline this year — El Nino fueling an active eastern Pacific hurricane season; a marine heat wave; and an astronomical alignment that happens only once every 20 years.
Total water levels this week in Los Angeles, Orange and San Diego counties could reach more than 8 feet above the baseline, which is defined as the average daily lowest water level observed between 1983 and 2001.
The record for highest seawater level ever recorded in La Jolla is 7.81 feet, set on Nov. 25, 2015, during the last “very strong” El Niño, according to the weather service’s San Diego office. On Sunday, the level reached 7.66 feet.
The record for the highest-ever seawater level at Los Angeles Harbor is 7.92 feet, recorded on Jan. 10, 2005, which occurred during a weak El Niño. Projected seawater levels at the harbor could hit 8.1 feet on Tuesday and 8 feet on Monday and Wednesday, the weather service office in Oxnard said. On Sunday, the seawater level hit a preliminary high of 7.71 feet.
In Newport Beach on Sunday, the seawater had already reached a high of 8 feet, city officials said. That’s 1.8 feet higher than what would be expected from the high tide alone. Potential seawater levels on the city’s coastline could reach 8.3 feet on Monday at 9:15 a.m., and 8.5 feet on Tuesday at 9:50 a.m. and Wednesday at 10:28 a.m.
Record-hot ocean-water temperatures off California are causing seawater levels to be 1.25 to 1.8 feet higher than they would be just from the movement of the moon, Earth and sun, scientists say. Ocean temperatures have been affected not only by human-caused climate change, but also an El Niño-fueled Kelvin wave and a months-old marine heat wave unrelated to El Niño.
A surface temperature reading of the ocean water at Scripps Pier in La Jolla, a neighborhood in San Diego, reached a high point for the year of around 77 degrees in early August; the average maximum is around 70 degrees. On Thursday, the surface temperature there was around 73 degrees, well above the average of 66 for this time of year.
Scientists warn that coastal flooding is expected to become increasingly worse later this year and into next year. Even higher tides are expected around the Thanksgiving, Christmas and Martin Luther King Jr. Day holidays — the so-called king tides that Californians expect every year.
However, these king tides will be exceptionally extreme, producing some of the highest tides due to astronomical reasons alone. That’s because we’re near the peaks of what are known as the 18.6-year lunar node tidal cycle and the 4.4-year lunar perigee tidal cycle, which arise from small changes in the orbit of the moon and affect tide-generating forces, according to Reinhard Flick, a researcher at the Scripps Institution of Oceanography at UC San Diego.
If big storms emerge during those king tide events around Thanksgiving, Christmas and the Martin Luther King Jr. Day holidays, they will further worsen the coastal flooding risk, scientists warn.
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