Boston Built a $20 Billion Neighborhood on Mud Flats, and Now 99% of It Faces Flooding by 2050

$343 Million in Tax Revenue, Built on Fill Dirt Barely Above Sea Level

The Seaport sends $343 million a year back to the City of Boston in property taxes. That money funds the police department, Public Works, the Public Health Commission, and a share of every essential city service.

It comes from less than 4 percent of Boston’s total land.

Nearly $20 billion in real estate now sits on what was, just decades ago, a wasteland of parking lots and abandoned warehouses. Before that, it was tidal marsh and mud flats. Developers filled it in, built the land just above the highest recorded high tide, and turned it into a neighborhood of biotech labs, luxury condos with rents above $4,000 a month, and headquarters for Amazon, Fidelity Investments, and Vertex Pharmaceuticals.

The Metropolitan Area Planning Council found that 99 percent of what has been built in the Seaport since 2000 faces flood risk by 2050.

“Everyone knew that there was a risk in developing that area,” longtime civic leader Ted Landsmark told the Boston Globe.

They built it anyway.

The Buildings Might Survive. The Streets Won’t.

Many Seaport developers point out that their buildings were designed to handle flooding. Elevated lobbies. Flood-resistant ground floors. Mechanical systems placed above projected waterlines.

None of that matters if the roads, tunnels, and storm drains connecting those buildings to the rest of Boston go underwater.

Derek Anderson, who leads civil and water engineering work in Boston for Arup, a multinational consultancy, described what the Seaport could look like in coming decades: a patchwork of flood-proofed buildings surrounded by submerged streets, water deep enough for people to kayak through.

“When private developers say, ‘We’ve made our buildings resilient,’ they’re not talking about making the neighborhood resilient,” Anderson said.

Boston Harbor already floods the Seaport and surrounding areas roughly a dozen times a year, according to NOAA. Fifty years ago, that number was two or three.

By 2030, a single nor’easter could cause up to $1.2 billion in damage in South Boston alone.

The Clock Is Running on a Plan That Won’t Break Ground Until 2030

The City of Boston and the U.S. Army Corps of Engineers are in the middle of a $6 million study of Boston’s 47-mile coastline. A draft report is expected this spring. A final version is targeted for fall 2027. A request to Congress for construction funding would follow in 2028 or 2029.

Construction of flood protection projects likely will not finish until around 2040.

The total cost to protect the coastline could exceed $10 billion, based on estimates from similar projects in New York and San Francisco. Boston cannot cover that alone.

Meanwhile, the federal funding pipeline for Army Corps projects faces uncertainty. The Trump administration’s Office of Management and Budget paused $11 billion in Army Corps projects earlier this year, and the Boston study, already halfway done, could be affected.

Jeff Herzog, program manager for the Army Corps’ New England District, put the urgency plainly: “Some of these flood pathways are anticipated to be a problem by 2030, so it’s important to start today to prepare for those immediate, near-term risks.”

What Happens to the Rest of Boston if the Seaport Goes Under

This is not just a Seaport problem. One in seven Bostonians, roughly 100,000 people, could face flood exposure by the 2050s, according to Arup. Flooding that enters South Boston could roll inland into Roxbury and the South End along well-documented flood pathways.

About 9,000 residents across downtown, East Boston, South Boston, and the South End could be forced to leave their homes and seek public shelter during a major flood event.

By mid-century, Boston could see 3,000 properties damaged by flooding every year, costing an estimated $62 million annually, 75 percent more than current levels, according to the First Street Foundation.

If Seaport property values drop, tax revenue drops with them. The $343 million the Seaport generates does not stay in the Seaport. It pays for services citywide, from Charlestown to Hyde Park.

Paul Kirshen, a University of Massachusetts Boston professor who has studied climate adaptation for decades, did not mince words about how the neighborhood was planned.

“It could have been a shining example of how to do it right,” Kirshen said. “But it became a shining example of how to do it wrong.”