Big waves drive ocean flooding

Children in the Uliga area of Majuro watch as a high tide driven by unusually high offshore waves caused ocean inundation around Majuro Atoll last week. Photo: Hilary Hosia.

GIFF JOHNSON
Over 200 people evacuated their homes in the capital of the Marshall Islands as big waves caused ocean inundation around the atoll November 27.

The ocean flooding was caused by high waves that combined with an otherwise unremarkable high tide twice Wednesday, with ongoing, but smaller inundations Thursday and Friday before the tides receded.

“The predicted tides were not particularly high, certainly not in the vicinity of the record high water levels from September of this year (that produced a series of ocean inundations in Majuro),” said climate researcher Dr. Murray Ford, a senior lecturer in Geography at the University of Auckland. “The tides and sea level rise component is not unusually high and not the direct cause of this flooding.” Ford, who previously worked at the College of the Marshall Islands, said it was only a “contributing factor.”

“The key driver of this current inundation appears to be a large swell which has arrived from a more northerly direction than the typical trade wind swell,” Ford said.
Although damage appeared modest around Majuro Atoll, people’s homes and yards were flooded with ocean water, roads at the international airport were temporarily impassible during peak flooding late afternoon Wednesday, and debris ranging from rocks and sand to garbage rolled onto roads and into yards requiring extensive clean up work.

Marshall Islands Red Cross official Harry Herming said 185 Majuro residents were relocated from flooded areas to two local elementary schools, while the Church of Latter-day Saints, Salvation Army and Ahmadiyya Muslim Community all opened their doors to additional local residents in need.

Driving the flooding were ocean waves averaging nearly five meters in height (16-feet).
A buoy located in the ocean near Majuro monitors waves, providing researchers a wealth of oceanographic data for nearly 10 years. “It is looking like these are the largest waves recorded by the buoy which has been in place on and off since April 2010,” said Ford.
“This particular event would be best described as a large swell, meeting a high, but not unusually high tide,” Ford said. “No swell and these tidal levels wouldn’t have been a problem.”

The ocean flooding last Wednesday was “made worse” because the wave swell hit Majuro from a more northerly direction. “We’ve found, and locally surfers seem to know, that swells coming from the north can thread the needle through the pass and enter the lagoon more freely than a north easterly swell, which doesn’t enter through the pass as easily,” said Ford.Historically, the king tide period for the Marshall Islands is January to March.


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