9 april 2018

Sea Level Rise Could Add Up to Gridlock, and Sooner Than You Think

The severe coastal flooding brought by storms in January and March has drawn renewed attention to the issue of sea level rise, and how prepared or unprepared we are for it.

WCAI - Local NPR for the Cape, Coast & Islands, April 9, 2018

A new series of local sea level report cards, put together by researchers at the Virginia Institute of Marine Sciences, concludes that Boston should prepare for water levels in 2050 to be a foot and a half higher than they are today. Molly Mitchell, a marine scientist at Virginia Institute of Marine Sciences Center for Coastal Resources Management, says that number is high, even for the east coast.

“The trend over the last forty years has been not particularly high, certainly nothing like what’s been going on along the Gulf Coast,” Mitchell explained. “But the acceleration in that trend has been very, very high. And that’s what’s driving the high projection for 2050.”

That projection could help developers and local regulators make better choices about where and how to build homes or infrastructure. For example, Mitchell says that many coastal areas are rethinking how they set base flood elevation – the lowest elevation at which a home or other building could be built.

“That, currently, is based in most areas on past flooding events,” said Mitchell. “There are localities that are starting to look at that and say ‘You know what? We want to look at what the water is going to be like in thirty years and add that into our base flood elevation, so that we’re not building houses that will have to be elevated in thirty years.’”

Coastal roads are another concern. A new analysis by University of New Hampshire scientists finds that more than 7,500 miles of coastal roadways, including over 400 miles of interstate highways, face the threat of regular flooding at high tide.

“That’s a lot of roads,” said Jennifer Jacobs, a professor of civil and environmental engineering at UNH and director of the Infrastructure and Climate Network.

Flooding that happens in the course of normal high tides is known as nuisance flooding, and the UNH researchers found that the East coast has already seen a 90% increase in such flooding over the past two decades. That will only get worse as the water level continues to rise.

Massachusetts is nowhere near as vulnerable as Florida or North Carolina, in this regard. Still, the team found that 240 miles – 0.5% of all roads in the Commonwealth – are at risk for nuisance flooding in coming years.

While calling it a nuisance may make it seem like no big deal, Jacobs says the impacts of regular flooding can be huge. First of all, there are the coastal roads that provide essential access to homes or for emergency vehicles.

And then, there are the delays. By 2020, nuisance flooding could account for 160 million vehicle-hours of delays up and down the East Coast – a dramatic 85% increase since 2010.

“This is not a Boston or Cape Cod problem, or a Hampton Roads or Miami problem,” Jacobs said. “This is a United States problem.”

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