BOSTON — Famous for its role in America’s war for independence, this city is now fighting the rising seas.
Boston is raising streets, building berms and even requiring that new high-rise condominium developments on its harbor acquire “aqua fences” — portable metal barriers that can be dragged to the street and anchored to the pavement to deflect incoming waves.
Mayor Martin Walsh, a Democrat, has vowed to spend more than $30 million a year, equal to 10% of Boston’s five-year capital budget, to defend the city from a watery future that is expected because of climate change.
“People talk about a managed retreat” for waterfront cities, said Boston’s chief of environment, energy and open spaces, Christopher Cook, as he looked out on the city skyline from a popular waterside park across the harbor. “Where do we retreat to?”
Though Florida, Louisiana and the Carolinas are frequently associated with flooding, Boston was ranked the world’s eighth most vulnerable to floods among 136 coastal cities by a 2013 study produced by the Organization for Economic Cooperation and Development.
The sea that surrounds Boston crept up nine inches in the 20th century and is advancing ever faster toward the heart of the city.
And as climate change accelerates, the pace of sea-level rise in Boston is expected to triple, adding eight inches over 2000 levels by 2030, according to a report commissioned by the city. The ocean might climb as much as three feet above 2013 levels by 2070, the report said.
As much as or more than any other coastal city in the country, Boston is confronting this existential threat and is taking steps now to contain the problem — at a relatively affordable price and within a short timeline.
A surging sea could wreak havoc in a place where half the city is built on low-lying landfill. Among the vulnerable spots are commercial piers, Logan International Airport, low-income neighborhoods in the South End, the New England Aquarium and pricey apartment buildings in the newly redeveloped Seaport area. The effects are evident already; seawater at high tide has lapped up onto some streets on days even when the sun is shining.
Even in a city that is trying to grapple with the problem, the challenge is enormous. Greenhouse gases are global, but the impact of climate change is local.
Boston’s low-income neighborhoods, where public housing projects were built on landfill, are particularly vulnerable to flooding. By the end of the century, a large part of the Dorchester neighborhood, which on its own would be the fourth-largest city in Massachusetts, could be underwater.
“If there is a finite amount of resources and a finite amount of time, we have to be intentional about protecting our most vulnerable residents,” Cook said.
Boston already has discarded the most expensive alternative.
The University of Massachusetts at Boston and the Woods Hole Group, an environmental and scientific consulting firm, had studied the possibility of building a massive harbor barrier similar to those in the low-lying Netherlands or the one across the River Thames in London. It estimated that construction would cost as much as $11.8 billion, not counting miles of structures and berms needed to prevent water from outflanking the new barrier. And that price would not include the costs of interference with shipping and ecological damage from dredging and altered currents.
In New York City, the U.S. Army Corps of Engineers is studying a $119 billion barrier to protect against rising seas and more-destructive storms, such as Hurricane Sandy, the 2012 “super storm” that flooded Lower Manhattan, tunnels and subway lines and cut off electricity. In January, President Donald Trump criticized the idea in a tweet, calling it a “200 Billion Dollar Sea Wall” that is “costly, foolish [and an] environmentally unfriendly idea that, when needed, probably won’t work anyway.”
“It will also look terrible,” he added. “Sorry, you’ll just have to get your mops & buckets ready!”
Boston’s projects are more modest in scale but no less crucial. In Charlestown, the city plans to raise Main Street by about two feet at an estimated cost of as much as $3 million. The taller structure would block the main flood pathway and protect more than 250 residences and 60 businesses.
The Massachusetts Bay Transportation Authority is spending $22 million to build watertight steel doors that can be closed at the entrance of a rail tunnel near Fenway Park. And the MBTA also plans to tear out a heavy glass-brick cube protecting an underground rail ventilation system near its Aquarium stop and replace it with brick and steel-reinforced concrete.
Cook is scouring waterside parks for places where changes in elevation can be turned into natural barriers.
That’s why Joe Moakley Park, a 60-acre area in South Boston across the street from a beach, is important, Cook said. The park floods regularly, forcing the cancellation of sporting events at its playing fields. Moreover, rising sea levels are turning the park into a major flood pathway that in another decade could contribute to the inundation of nearby neighborhoods, including two low-income housing developments. And it is built on landfill, making it “very, very vulnerable,” Cook said.
So the city is looking at building a flood protection berm as high as 10 feet along the shore, raising the level of the park and installing large chambers beneath the playing fields to hold 5 million cubic feet of stormwater. The package would include improved recreation areas.
Similar plans have been drawn up for Ryan Playground in the Charlestown neighborhood on the Mystic River.
These shoreline plans are flexible, an advantage in preparing for widely different, still-uncertain climate scenarios.
“What Boston and other communities are doing is trying to be proactive,” said Nasser Brahim, the technical leader on vulnerability assessment and adaptation planning at the consulting firm Kleinfelder, which is advising the city. “You never know when a disaster is going to hit.”
The rise in sea levels has two main drivers: the melting of ice sheets in Greenland and Antarctica; and “thermal expansion,” meaning that warm water has greater volume than cool water.
The result will be a global sea-level rise of more than 10 inches by 2100 if temperatures stay within the two degrees Celsius (3.6 degrees Fahrenheit) target set in the Paris accord, an international agreement signed in 2015.
Other scenarios are more alarming. The Boston government has a slide presentation with a bar chart representing a 7-foot, 4-inch rise in sea levels by 2100 if worldwide carbon emissions continue to climb. Next to the bar stands a drawing of former Boston Celtics basketball star Kevin Garnett, who is a few inches short of the 7-foot-4 mark.
The forecast numbers all have substantial margins of error, but even the smallest rise is threatening.
Rising sea levels have already increased the frequency of flooding from relatively normal tides and rainfalls. In 2017, Boston saw a record 22 days with high-tide flooding, according to the National Oceanic and Atmospheric Administration. The city could also experience more “blue sky” flooding, when seawater laps onto streets during high tides on sunny days.
For an academic paper on water levels in Boston’s harbor, three scientists ferreted out correspondence and measurements made as early as 1825 by Loammi Baldwin Jr., a civil engineer commissioned to construct a dry dock at the Charlestown Navy Yard.
They concluded that sea level rise in Boston began to pick up speed only after 1940. One-third of the 100 most extreme storm events took place in the past dozen years, including in 2018, which saw some of the highest water levels measured since European colonization, they wrote. By the 2030s, the city will face an “abruptly” elevated risk of coastal flooding when tides shift, the scientists said.
For many cities, floods that once occurred every 100 years are expected to become annual events — or even more frequent — by 2050, said Michael Oppenheimer, a professor of geosciences and international affairs at Princeton University.
“Enough is known to start formulating policies to make the coast more resilient and to adapt to anticipated sea-level rise,” he said.
Boston is one of 94 cities worldwide sharing information about how to deal with climate change.
In the end, Oppenheimer warned, retreat might be the only option. “It is what a lot of cities will have to do because a lot of neighborhoods are not defensible,” he said. Sea levels will continue to rise, no matter how high the coastal barriers might be, he said.
“You either protect people or you get them out of the way,” he said. “There just isn’t a choice.”
An MBTA bus depot in the Charlestown neighborhood is one potential trouble spot. The buses there serve nearly 100,000 people, but the depot stands on landfill and is inundated during heavy rain. With higher sea levels, severe storms could cause enough flooding to frequently knock out bus service. And even if an existing wall is raised, water could still creep in from another side.
Practical problems abound. When the MBTA wanted to install a temporary wall farther into the Mystic River to allow construction onshore, the agency discovered that the soil in the area was made of weak marine sediments. Next, the engineers discovered two large-capacity electric power lines critical to keeping the region’s lights on. The utility did not want to move them.
Eventually, the MBTA laid down a stone embankment to hold up the existing wall. It is 5.4 inches higher than the city requires, and grasses were planted on top to improve its appearance from the river and a nearby bridge.
Other agencies face daunting challenges. The Boston Water and Sewer Commission designs storm sewers to cope with as much as 4.8 inches of rain in 24 hours. That capacity covers 90% of the storms that occur in an average year. But climate change is increasing the size and intensity of rainfalls, which by 2100 could dump as much as 6.65 inches onto the city in a 24-hour period.
The neighborhood along the edge of the Fort Point Channel, which feeds into Boston Harbor, also shows gains and tasks ahead.
General Electric has leased two historic brick buildings in the neighborhood that will become the company’s slimmed-down global headquarters. GE has elevated the first floor of the building at Necco Court, installed systems to capture and reuse rainwater, and moved the electrical equipment to a platform several feet higher than the basement floor.
From the Harborwalk — a pedestrian path along the piers, wharves and shoreline around Boston Harbor — it is seven steps up to the sidewalk that leads to GE’s building at Necco Court. When Brahim stands next to the equipment platform, it starts at the height of his shoulder.
A short distance along the Harborwalk, the city insisted that the Boston Children’s Museum turn the lawn beside its building into Martin’s Park by installing benches, mounds of earth with plants and a tiny hillside playground.
In many cases, the city can require tougher flood standards because developers are seeking zoning changes to reclassify property on South Harbor piers from industrial to commercial or residential use. And Cook notes that the 47-mile Harborwalk gives the city easements in most areas.
Yet much remains undone. GE had planned on building a 12-story headquarters, but to ease financial pressures, the ailing conglomerate sold the site, which remains vacant. Brahim said it isn’t clear what the new developer is planning. And the electrical equipment of a brick building next door remains in a vulnerable spot below the level of the Harborwalk.
Nearby, some developers have opted for other defensive measures.
At 300 Pier 4 Blvd, a new luxury apartment building on the water’s edge a short walk from the children’s museum, the building manager keeps in the basement 16 crates, each with 10 portable “aqua fences” designed to block water. If the weather forecast is ominous, a Bobcat loader will carry the roughly four-foot-high barriers outside to be fastened to steel buttons installed in the stone sidewalks. Metal legs are supposed to hold the barriers upright, and tubing will help to seal them against the advancing waters.
The system must be tested annually — or the building will lose its insurance. This year, in the first drill, it took 15 to 20 workers eight hours to assemble the barrier.
“I think it will do what it was designed for,” said Jeremy Diflaminies, the general manager of 300 Pier 4 Blvd.
Old buildings and the poor
There are no seawalls where most of Boston’s poorest residents live.
“Your most vulnerable citizens are more likely to bear the burden of climate change disproportionately, so if we don’t provide climate adaptation plans, you’re doing more of our people a disservice,” Cook said.
In areas that are being redeveloped, such as East Boston, most first floors of new buildings are higher than is required by the Federal Emergency Management Agency or state codes, Brahim said. But older residential buildings are occupied by lower-income people, most of whom do not have the money to alter the topography.
The new buildings “end up being islands of resilience,” Brahim said. “If a building itself is being raised, it could act as a barrier, but only if the surrounding landscape is being raised.”
For now, he says, new standards are being imposed on new buildings in the hope that eventually “as projects come on, they will build up to something bigger.”
Cook drove a visitor along Joe Moakley Park in South Boston, the large flat area across from Old Harbor that would not offer much of a defense for some subsidized housing that is vulnerable to rising seas. He talked about changing the contours of the expanse.
Then, he drove through a tunnel under the harbor to East Boston, where newcomers are moving in while others remain on the first steps of the economic ladder. The latter are the people “who in a climate emergency can’t evacuate,” Cook said. “These aren’t people who can relocate to the family home in the mountains. These are people in public housing.”
Walsh, the mayor, is keenly aware of the inequities linked to climate change, and he has focused on areas where the city’s poorest residents live.
Cook pulls his electric vehicle into the parking lot of a Shaw’s supermarket, the only big grocery store in East Boston. Cook positions his car to face a pier lashed by wintry weather and the 10-foot tides of Boston Harbor. Below the level of the parking lot is the Shaw’s loading dock. Almost every time there is an exceptionally high tide known as a king tide, the loading dock floods.
“When we think of vital infrastructure, we [need to] think of a grocery store,” Cook said. “This is the opportunity right here.”