If you think there are coastal flooding problems in the region now, just wait — it’s going to get a whole lot worse, according to a study released by the U.S. Geological Survey.
Scientists have found that the local coastline is part of a unique, 600-mile-long “hot spot” along the Atlantic Coast where sea levels are rising at a significantly faster rate than the world as a whole — three to four times faster. The hot spot stretches down the Atlantic Coast from north of Boston to North Carolina.
“Flooding right now is an annoyance, but it will be more of an annoyance and bad enough that you’ll think twice about parking your car in the driveway if there’s a storm coming and it’s the spring tide,” said Peter Howd, a co-author on the study and a contracted oceanographer with the U.S. Geological Survey.
Since about 1990, sea-level rise in the 600-mile hot spot has increased 2 to 3.7 millimeters per year; the global increase over the same period was 0.6 to 1 millimeter per year, according to the study. As a result, scientists predict that sea levels in the northeast Atlantic will rise 8 to 11.4 inches more than the global average by 2100. That is over and above the 2- to 3-foot rise in sea level that many scientists expect to occur globally over that span.
Although north of Boston is “on the low end of the range we’re talking about,” the area is still facing a dramatic increase in the number of significant flooding events, Howd said.
“That additional 1 foot of water could be enough so that smaller storms cause chronic coastal flooding, as opposed to an acute event like a hurricane,” said Howd, who has family on the North Shore.
This isn’t the first report to predict drastic changes to the local coastline. Last year a U.S.G.S. report predicted that much of the Great Marsh will disappear over the course of the next century, as rising sea levels flood it. The Great Marsh extends from Gloucester in the south to Hampton, N.H., in the north, encompassing all of the coastline off greater Newburyport.
And next month, new flood insurance maps will go into effect that greatly extend the zones in which severe coastal flooding may occur. Most homes on Plum Island and Salisbury Beach will now be located in these zones, which will require them to purchase federal flood insurance if the home has a bank mortgage on it.
But there is no comprehensive plan in place to handle rising sea levels, at least not yet.
That’s not unexpected or unreasonable, said Martin Pillsbury, director of environmental planning at the Metropolitan Area Planning Council.
“Most communities don’t have the chance to dig in and take stock of this because they are more focused on the short term, the budget crunches and all of the other things you have to get done on a local level,” Pillsbury said. “There are so many short-term problems and pressures that if you can put it on the back burner, that’s what will happen.”
About a month ago, the planning council received authorization to use $80,000 from a federal grant to develop what it calls the Regional Climate Change Adaptation Strategy. The purpose is to help communities figure out what they can and should be doing to prepare for the changing environment and rising seas.
“We frame the issue through the concept of resiliency: What can you do to become more resilient to the impacts?” Pillsbury said.
Part of the program will be to conduct a vulnerability assessment using existing data to determine more specific implications of higher sea levels and climate change for eastern Massachusetts. The MAPC will also research best practices and policies from cities such as Boston and New York City — which are further along in preparing for higher sea levels — and adapting them to fit smaller communities on the North Shore.
Boston, for instance, is already taking inventory of low-lying areas, is inspecting thousands of sewer and storm drains, has instructed departments to take rising water levels into account during planning, and has taken measures to help businesses prepare for higher seas.
Eventually, many cities and towns along the coast may have to adjust their own land use and development regulations, invest in reinforcing existing infrastructure, and set aside money to identify areas that are most at risk, Pillsbury said.
“We envision distributing publications, sort of a tool kit or how-to guide to get a community started. This will be a long-term process, because it is a long-term issue,” he said. “Most communities are concerned with this and know it’s out there and know it is getting more urgent. We’re just trying to find a way to help them get started.”
Ocean levels do not rise at the same rate in every part of the world. A number of variables, including strength of ocean currents, water temperatures, ocean circulation and salt levels, play a part, according to the study.
Unfortunately, it seems the rate the ocean is rising is only expected to keep increasing in this region.
“Based on what our models are saying, there is pretty good agreement that the signal (fastest rates of acceleration) is moving north,” Howd said.
In lay terms, the sea-rise rates are tied to the speed of circulation in the Atlantic Ocean. As more ice melts in Greenland, the water becomes colder, slowing down circulation even more and increasing the rate in which ocean levels rise around the northeast coast, he said.