Artificial system

An idea to reduce coastal flooding in Boston: create an artificial wetland

Chained between rusty beams on Chelsea Creek in East Boston is a large ball of floating plants.

It is made of wood shavings covered in coir and netting, with marsh grass growing on top and seaweed below. And it’s heavy; the pod weighs about a ton when waterlogged.

This floating ball is part of a trial for a new climate resilience project: The Emerald Tutu. It is a system of floating wetlands designed to reduce coastal flooding by reversing waves. Boston is expected to experience increased flooding over the next few decades due to climate change.

“Basically, it’s like a giant sponge that fits around urban coastlines like we have here in Boston,” said Gabriel Cira, the project manager. “It protects these coasts from the intense effects of coastal storms.”

Tufts of marsh grass stick out of an Emerald Tutu pod as staff in kayaks maneuver it between the uprights of a pier on Chelsea Creek, where they will anchor it. (Robin Lubbock/WBUR)

Of course, the actual function of the Tutu is a bit more complicated than the sponge in your kitchen sink. In theory, hundreds of individual modules would be linked together and anchored to the ocean floor. As the waves passed through, they would first hit these clusters, lose energy, and then come in smaller and with less force.

Because they are made up of individual plant balls, the system can also adapt to different types of shorelines.

“We can add more, we can add less, we can bring them closer, we can drive them away,” said Julia Hopkins, coastal engineer and lead scientist on the project. “We can maintain it in such a way that you can keep pace with storms, sea level rise and events that would occur with climate change.”

The test unit at Chelsea Creek is the latest iteration of the project, which was originally developed as the winning entry for the 2018 MIT Climate Changed Ideas Competition. The research team later received a grant from the National Science Foundation .

They’ve since managed to figure out how to arrange the pods to reduce waves in tests in Oregon, where researchers hit strings of plant balls with waves from a simulator. The pod in East Boston is expected to remain in place for several months, and the team plans to conduct larger-scale testing of linked pods over the coming year.

Gabriel Cira, Emerald Tutu project manager, with a test module destined for Chelsea Creek.  (Robin Lubbock/WBUR)
Gabriel Cira, Emerald Tutu project manager, with a test module destined for Chelsea Creek. (Robin Lubbock/WBUR)
Emerald Tutu coastal hydrology expert Dr. Julia Hopkins at Chelsea Creek.  (Robin Lubbock/WBUR)
Emerald Tutu coastal hydrology expert Dr. Julia Hopkins at Chelsea Creek. (Robin Lubbock/WBUR)

East Boston is one of the city’s most prone neighborhoods to the type of flooding that the Tutu tries to solve.

At the Shaw supermarket near Liberty Plaza, John Walkey, director of climate justice and shoreline initiatives at GreenRoots, pointed to the short distance between the parking lot and the water line.

“This happens to be one of the flood paths identified by the City of Boston,” he said. “Seawater comes in straight in…so ducks and geese will kind of float in the parking lot and keep floating in a parking spot.”

A recent UMass Boston report found that the city could experience high tide flooding – also called nuisance flooding – on average 180 days per year by 2050; right now we see this kind of flooding about 15 days a year.

“Twenty or thirty years from now, Liberty Plaza is flooded, parts of Maverick Square are flooded, the Sumner and Callahan tunnels are flooded,” said Paul Kirshen, professor of climate adaptation at UMass Boston and one of the co-authors. of the report. “Instead of being an occasional nuisance, it would happen often.”

John Walkey, Waterfront Initiative Coordinator for GreenRoots Chelsea, at Belle Isle Marsh.  (Robin Lubbock/WBUR)
John Walkey, Waterfront Initiative Coordinator for GreenRoots Chelsea, at Belle Isle Marsh. (Robin Lubbock/WBUR)

East Boston is an environmental justice community. In addition to flooding, residents face higher rates of air pollution, asthma and chronic heat. The neighborhood has also been a hub for low-income and immigrant communities. Although it has gentrified with increased development, East Boston has a lower median household income than the rest of the city and the highest percentage of immigrants.

There are also vestiges here left by polluting industries; the Emerald Tutu team tests their new pod at the Hess site, named after the Amerada Hess Corporation which once owned the area and used it as a fuel tank farm. The East Boston Community Development Corporation now owns the site and has provided access to researchers.

Due to this history and the severity of climate issues, there is added pressure to ensure that the Tutu not only performs as intended, but also accommodates the local community.

“There are developers and people in the city and then people from community organizations who suddenly go out to community members and say ‘we want to know what you think and what your vision is for East Boston in 15 year ? “, Valkey said. “And you’re talking to someone who thinks they might not be able to stay in their apartment for the next month. So there’s a disconnect.

Emerald Tutu researchers have taken steps to close this gap. They have now worked in East Boston for several years and have attended several community meetings to share the project. They also reached out to GreenRoots and other local organizations that have long worked in East Boston on climate and accessibility issues.

A team of Emerald Tutu staff and volunteers launches a module at Chelsea Creek.  (Robin Lubbock/WBUR)
A team of Emerald Tutu staff and volunteers launches a module at Chelsea Creek. (Robin Lubbock/WBUR)
An Emerald Tutu module anchored in place at Chelsea Creek by three ropes running through the middle of the module.  (Robin Lubbock/WBUR)
An Emerald Tutu module anchored in place at Chelsea Creek by three ropes running through the middle of the module. (Robin Lubbock/WBUR)

One such organization was Eastie Farm; Cira was the architect of the association’s new climate-friendly greenhouse. Farm manager Kannan Thiruvengadam and several other volunteers were part of the group that helped set up the Tutu pod in early July.

“I was excited to see how it goes,” Thiruvengadam said, “and when you’re there and another pair of hands are needed, you want to help out.”

Thiruvengadam is optimistic about the Emerald Tutu and the role it could play in East Boston’s future. Part of the group’s mission is to provide opportunities for citizen science and potential local jobs on production and maintenance if the full system works.

But this final goal is still a long way off. The Tutu is at least a few years away from being operational, and researchers still have more tests to perform.

No one thinks the Emerald Tutu will be the silver bullet that will save East Boston from climate change.

Floating wetlands have been used in other states to improve water quality and habitat, but they are not historically designed for flood protection. The system can’t stop sea level rise – Boston has one of the highest rates of sea level rise in the world and is expected to see a 4.8ft rise by the end of the century – and there are questions about how the pods will withstand a severe storm.

Graph of projected sea level rise in Boston (Courtesy of Professor Paul Kirshen, UMass Boston)
Graph of projected sea level rise in Boston (Courtesy of Professor Paul Kirshen, UMass Boston)

The problems facing East Boston and the rest of the city are serious. In addition to community plans like the Emerald Tutu, the City of Boston has plans for berms, elevated walkways, and a deployable seawall to block off part of the neighborhood’s greenway.

“It’s all on deck,” said UMass Boston’s Paul Kirshen, “any reasonable idea should be considered.”

For many watching the emerald tutu take shape, there is hope that one day it will be just one solution among many.