Boston completes plans to strengthen all 47 miles of coastline against flooding

Water from Boston Harbor floods Long Wharf during a storm surge in 2018. Craig F. Walker/Boston Globe

With the completion of a recent study focusing on Charlestown and East Boston, every part of the city’s coastline has been studied.

By Ross Cristantiello – August 14, 2022

Coastal flooding is a legitimate threat to the safety of many Boston residents, and the likelihood of flooding in the city will only increase over the coming years, according to an extensive new report released by city officials. That report is the product of years of work studying Boston’s coastline and determining the best ways to protect it. Now, the city has officially developed coastal resilience plans for all 47-miles of its coastline.

Coastal resilience, as defined by the National Ocean Service, is “the ability of a community to ‘bounce back’ after hazardous events such as hurricanes, coastal storms, and flooding – rather than simply reacting to impacts.”

Other results of climate change, like the severe drought persisting throughout the state, may be on the minds of many this summer. But the risk of flooding is real, and officials are mapping out how to decrease flooding for decades to come.

“Climate adaptation presents an opportunity to create a resilient, climate-ready waterfront that advances priorities for open space, mobility, affordable housing, social and racial equity, and natural resource conservation,” said Mayor Michelle Wu in a statement. “This report lays out a community-driven vision for Boston’s coastline to be resilient, accessible, and protected.”

How serious of a problem is coastal flooding?

The term “coastal flooding” encompasses both regular flooding caused by rising sea levels, as well as flooding caused by major storms.

Right now, experts predict that the sea level will rise nine inches by the 2030s and 36 inches around the 2070s if emissions continue at their current pace, according to the report. The gradual sinking of the land will also play a role, exacerbating the problem.

In the short term, given the sea level predictions, a flood event inundating five percent of the city will have just a one percent chance of occurring in a given year. But by the 2050s, that type of flood will be ten times more likely. And by the 2070s, that level of flooding is projected to occur at least once per month, according to the report.

The most recent work published by the city focused on East Boston and Charlestown, two of the most vulnerable areas of Boston. Right now, the most significant flood pathway in East Boston starts near the Blue Line’s Maverick Station and flows inland via the East Boston greenway. Flooding is expected to increase along Chelsea Creek, Belle Isle Marsh, and Coleridge Street near Constitution Beach over the next decade. This will create new flood pathways that will intersect and combine to endanger thousands of residents, businesses, and transportation infrastructure. The fact that new flood pathways could be created, instead of existing ones simply experiencing more action, heightens the complexity of coastal resilience planning.

Several areas of Charlestown are also at risk right now. Low-lying sections of ground in the Navy Yard surrounding Constitution Wharf, the Boston National Historical Park, and the 1st Avenue Corridor all get flooding from time to time. Most of the neighborhood’s flooding today enters near Ryan Playground and the Schrafft’s Center, according to the report. In the 2030s, all these areas will be more at risk, including additional risks to the Boston Autoport, particularly on the eastern side. New flood pathways could open up from the Little Mystic Channel and merge with flood pathways from the Navy Yard, endangering the CharlesNewtown and Bunker Hill affordable housing developments.

“East Boston and Charlestown are two of the most vulnerable neighborhoods to flooding and sea-level rise due to climate change,” said District 1 City Councilor Gabriela Coletta in a statement. “We have to act with urgency to fortify our waterfront and deploy nature-based solutions in order to protect the resiliency of our coastline and our people.”

Coastal resilience solutions

So, if flooding will get worse over the next 50 years, what can be done to protect Boston? Scientists have presented many innovative solutions, including the “Emerald Tutu” from a team at Northeastern University. This would create a network of environmentally-friendly circular mats of vegetation in Boston’s waters. The mats would be interlaced with pedestrian walkways, and are designed to emulate the ways that vegetation naturally protects coastlines.

The recently-released report includes more coastal resilience solutions, designed both for the short-term and long-term. Each area of the city is unique, and the proper way to prevent flooding will differ depending on location.

The following are examples of ways that the city could strengthen its coastline, as outlined in the report:

  • Raised waterfront parks, or harborwalks. These can help block important flood pathways by increasing an area’s minimum elevation, making it harder for water to flow inland, according to the report. They have the added benefit of providing space for recreation and education. On top of that, these areas can incorporate new infrastructure aimed at dealing with other aspects of climate change, like extreme heat and rainfall.
  • Raised berms and dunes. These mounds of sand and earth are good solutions for areas where a new waterfront park cannot be built, either because of space restrictions or the existence of privately owned property. In some cases, the tops of berms and dunes can be wide enough to accommodate pathways and oceanside viewing areas.
  • Vertical floodwalls. These are thick, high walls made from concrete or other durable materials perfect for areas where space is significantly limited. Sometimes, the floodwalls can be buried or contained in other types of infrastructure like roadways.
  • Deployable floodgates and barriers. These are essentially floodwalls that have to be installed specifically in preparation for a flood or storm. In the report, researchers said this solution is not preferred due the difficulty of operating, maintaining, and storing the barriers.
  • Strategic retreat. This is a phased process of removing or relocating buildings and infrastructure while preventing the construction of new development projects in areas with a high flood risk. This is a solution for when floodwalls, berms, and other “perimeter protections” are not feasible.

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