Cambridge leads in efforts on climate resilience, though it also has the most at stake in the region

Cambridge has $30 billion in real estate at stake from flooding, and atop that are the tens of thousands of jobs and residents within those vulnerable areas of Cambridgeport, Kendall Square, Harvard and MIT, experts said at a March 27 presentation.

Nine key projects to elevate the shoreline are underway, including at two dams and at Somerville’s Draw 7 Park, but in terms of climate resilience strategies against that flooding “we’re at the very beginning – this is still a long slog in terms of permitting” and funding, city councillor Patty Nolan said as chair of the Health & Environment Committee meeting.

The fateful date in the presentations was 2070, but the presenters warned that given the expense and regional complication of the needed fixes, five decades isn’t much time. While Cambridge leads on interventions and is now in the position of providing technical help to neighboring communities, overall, projects took too long to get started as a result of a global delay.

“We were hoping to prevent climate change much longer than was realistic,” noted Julie Wormser, senior policy adviser with the Mystic River Watershed Association.

Climate change mitigation is a large concern to the city, particularly around preventing flooding. While parts of Cambridge have always been vulnerable to flooding – around a third of it is built on marsh – “we’re getting larger storms and more frequent storms,” said Kathy Watkins, the city’s commissioner of public works.

A river floods through it

There are two types of flooding: precipitation and coastal. Watkins said the emphasis was on coastal flooding over rainfall, because it’s become “clear the severity of it is just completely different proportionally than some of the precipitation events,” Watkins said.

This work has to be regional and shared among communities, because rivers go through so many towns, and what happens in one municipality affects its neighbors. “Even though there’s 12 communities that benefit from this, it’s really the yeoman’s work and benefit that goes to Cambridge, which is why Cambridge has been a real leader in this,” Wormser said.

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Cambridge co-founded the Resilient Mystic Collaborative in 2018 to fund and implement regional climate change measures. It now stretches from Cambridge as far north as Reading, and from Lexington to as far east as Winthrop. “We wouldn’t have even known of the problem without Cambridge,” Wormser said, also crediting the city with technical, political and staffing support it has given the Charles River and Mystic River communities.

Since its founding, the collaborative has secured more than $127 million for projects focused on coastal and inland flooding, heat and social infrastructure, Wormser said.

If the dams overtop

The two dams that need to be improved are the Amelia Earhart Dam on the Mystic River between Somerville and Everett, and the Charles River Dam in Boston. Increased flooding levels mean both of these dams could be overtopped in the coming decades. There are $13 million dollars in ARPA funds that will be used to get to the point of construction for the Amelia Earhart Dam, which is owned by the state of Massachusetts. The Charles River Dam is owned by the Army Corps of Engineers, which means it is responsible for paying for upgrades, but this also means it will take longer to improve.

“We are luckily not the Gulf Coast, or Florida, or New Orleans or the Netherlands. We are not a bathtub,” Wormser said. “What kills people really is heat, not flooding. What degrades our communities is the flooding, but I don’t expect really major deaths from flooding,” she added.

Still, “if we do nothing, the dams overtop” and Cambridge floods, Wormser said. That travels up the Alewife Brook to the drinking water supply. “Cambridge, among other communities, couldn’t be Cambridge with this kind of saltwater flooding, because it’s so corrosive.”

Floods would affect more than 100,000 people and bring $60 billion in damage in the collaborative’s region – and around half that value is in Cambridge, Wormser said.

Rain and overflows

The city has also been working against precipitation flooding, such as by adding underground tanks on Hovey Avenue in Mid-Cambridge and in Parking Lot 6 in Central Square to capture stormwater. The parking lot tank can hold 400,000 gallons of stormwater at a time – and managed 3.5 million gallons of stormwater over all of 2021, Watkins said. This water goes into a pipe that discharges into the Charles River.

The city hopes to add an additional tank along Windsor Street in addition to a 1.25 million gallon stormwater tank and a 100,000 gallon stormwater bioretention system in the Tobin School project. The Port is one of the neighborhoods most at risk for flooding, which is why the city has put particular effort into flood control measures there, Watkins said.

There has also been work on reducing combined sewer overflows from pipes where stormwater and sewage combine. During storms, the sewage may overflow into rivers to prevent it from backing up into homes and businesses. Cambridge’s goal is to have all sewage be in separated pipes and ensure there is no water overflow during large storms. Since 1988, Cambridge, working with Boston and the Massachusetts Water Resources Authority, have reduced CSO discharge by 87 percent in the past quarter-century, according to Monday’s presentation.

A stronger

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