Local forecasters predict annual ‘king tides’ will have extra punch

Perfect storm of high tides, above-average sea levels, strong south swell could cause damage, flooding

High tides flood the parking lot of Kealia Pond in Maalaea last month. Scientists believe lingering conditions from an El Nino in 2015 have created higher-than-expected sea levels that, combined with high tides, put low-lying areas at risk. Photo courtesy of Tara Owens, Hawaii Sea Grant

It’s not unusual for Hawaii to see the highest tides of the year during the summer, but the ocean conditions that come with them this season could put coastal areas more at risk.

Known as “king tides,” this annual ocean event is expected along Hawaii beaches Thursday and Friday, as well as at the end of June and July. That, combined with above-average sea levels and a south swell forecast, has experts preaching caution.

“We can’t always predict exactly what localized impacts will be, so it’s helpful to spread awareness broadly so property owners and beachgoers can anticipate possible impacts,” said Tara Owens, coastal processes and hazards specialist with the University of Hawaii Sea Grant College Program. “Generally speaking, we could have serious flooding, wave runup, and/or erosion at any site in South or West Maui due to the combination of high sea level, high tide and south swell.”

Since April 2016, sea levels around the islands have consistently been higher than expected, said Owens, who’s also a liaison to the Maui County Planning Department. The Kahului Harbor gauge, for instance, has ranged from 3 to 9 inches above predicted levels, and some places in Hawaii have been 11 inches over. University of Hawaii scientists believe it’s related to the big El Nino that passed through in 2015, bringing large waves that washed over highways and further eroded West Maui shores.

“What happens when we have an El Nino is the trade winds die down,” Owens said. “They normally push water across the Pacific Ocean to the western Pacific. But when they die, some of the water from the western Pacific washes over to Hawaii . . . and temporarily raises sea levels. But, for some reason, we’re still experiencing those elevated sea levels as an impact of that event.”

Waves swallow a portion of the shoreline near Halama Street in Kihei last month. Low-lying areas of South and West Maui could be vulnerable this summer as king tides, the highest tides of the year, combine with above-average sea levels and a south swell around the islands. Photo courtesy of Tara Owens, Hawaii Sea Grant

Scientists didn’t fully realize the implications of this “sea level anomaly” until later.

“It was only after documenting them for this whole year that we realized we have this pool of warm water around us that’s sticking around, Owens said.

Then come the king tides. Tides rise and fall by the moon’s gravitational pull. When the sun and moon align, their combined forces create king tides, according to Sea Grant.

On Thursday and Friday, tide levels are predicted between 2 to 3 feet in locations throughout Maui County, according to the National Oceanic and Atmospheric Administration. Over those two days, Hana could experience the highest tides, from 2.87 to 2.92 feet. Meanwhile, Kahului could see tides from 2.73 to 2.78 feet, while Kihei and Maalaea Bay could get 2.57 to 2.62 feet and Lahaina could experience 2.43 to 2.48 feet. Molokai could see 2.65 to 2.69 feet at Kaunakakai Harbor and 2.52 to 2.56 feet at both Kamalo and Pukoo Harbors. Predictions for Kaumalapau on Lanai are 2.62 to 2.66 feet.

Most high tides will hit during late afternoon. NOAA expects them to return June 23 to 24 and July 21 to 22, again from 2 feet to just over 3 feet.

Any beach recently affected by waves or erosion “is especially vulnerable,” Owens said. That includes Kahana Beach and Honokowai/North Kaanapali in West Maui and the beach along Halama Street in Kihei. Wailea and Makena beaches are also “very exposed to south swell.”

Owens recommended moving valuable items in low-lying areas to higher ground. Canoes stored along beaches may need to be relocated. Boats should be secured in anticipation of both the swell and high tides.

Residents can help the University of Hawaii keep tabs on affected areas by submitting photos online or through a smartphone app. After setting up an account online at getliquid.io/home, search “HI Sea Grant” and join the dataset. Next, download the app (“liquid mobile data collection” for iPhone users and “Liquid Field Notes” for Android) and submit photos of high tide impacts. Photos from digital cameras can be uploaded to the website.

“These kind of events represent what we’re going to see more of in the future as sea levels continue to rise,” Owens said.

“Documenting the impacts is a really important thing we can do now to understand what those impacts will be.”

On Maui, there’s been a lot of erosion in recent years, especially during the last two winters, Owens explained. Michele Chouteau McLean, deputy director of the county Planning Department, said “the dynamic shoreline environment — not just king tides but episodic erosion, storm surge, etc.” are an ongoing concern.

“They all threaten public and private property, infrastructure and coastal resources,” McLean said. “While we have generally had effective shoreline management throughout the county, there are still significant areas that are vulnerable to these coastal hazards. We need to get ahead of the curve so that we are not playing defense as often as we do.”

For a six-day sea-level forecast, visit pacioos.hawaii.edu/shoreline-category/high sea. More information on king tides and how to participate in the citizen science program can be found at ccsr.seagrant.soest.hawaii.edu/king-tides.

* Colleen Uechi can be reached at cuechi@mauinews.com.


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