A pedestrian navigates Portland Pier in the wake of a flooding event. (Courtesy GMRI)
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December’s major storm, which caused heavy winds and significant flooding in parts of Portland, was one of the worst sea-level rise events the city has faced in over a century, local experts say.

The Gulf of Maine Research Institute, a Portland-based organization that studies ecological and environmental issues like sea-level rise and coastal erosion, conducted a study of the massive Dec. 23 storm that rocked the East Coast and left millions in the U.S. without power. 

According to a local expert, these types of events will be more frequent in the coming decades.

“Despite this past event feeling extraordinary, that type of flooding will be run of the mill by mid-to-late century,” said Hannah Baranes, a postdoctoral researcher at the Gulf of Maine Research Institute.

While the study found the storm surge itself “unspectacular,” the attendant sea-level rise was a major factor. It caused flooding around the city and hit during an already high tide.

Now known as a bomb cyclone, that event was called a “once in generation” storm by CNN.

Broadly speaking, Maine may have a good management plan in place, according to Baranes, an expert in sea-level rise and coastal hazards. But it likely won’t prevent increased flooding and one to one-and-a-half feet of sea-level rise in the coming decades.

“In a place like Portland where we are impacted by major winter storms, the truly big driver of flooding is the increase of baseline sea levels that the storms hit on top of,” Baranes said.

She added that the Oceanic and Atmospheric Administration has a tide gauge in Portland at the Ocean Gateway Pier, and found that on the morning of the storm, water level peaked at 13.7 feet above the mean lower low-water level, a way of tracking levels over time.

The city’s tide record gauge goes as far back as 1910. The Dec. 23 levels are roughly the same as those from the blizzard of 1978, according to Baranas, which ties it with the “highest water-level record” in the past 113 years.

“If we had not been experiencing sea-level rise over the past 100 years, the Blizzard of ’78 would have been the clear flood record-breaker, and this December storm would have been roughly a 1-in-10 year event,” Baranes said. 

A similar storm that hit Portland last January had a much higher surge, Baranas said, but came during lower tide, so it resulted in much less flooding.

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