Three feet of sea-level rise by 2070, averaging $1.39 billion in yearly flood damages, and much more during big storms.
That's perhaps the most dire prediction in Climate Ready Boston, a 407-page report on climate change released today by city officials. Using new data from a group of scientists overseen by the University of Massachusetts-Boston School for the Environment, the report says Boston is likely to see dangerous increases in flooding and extreme heat waves in the coming decades.
"Even under the most optimistic projections of global emissions reductions,” reads the report, “Boston faces serious risk from climate change and must adapt."
Climate Ready Boston forecasts about three to seven feet of sea-level rise in Boston by the end of the century, unless global greenhouse gas emissions are slashed dramatically. It also says the city could see heat-related deaths triple by 2050. And it predicts an increase in extreme storms that could cause inland flooding.
Three feet of sea-level rise would threaten much of the city, putting a fifth of South Boston underwater during high tide. Away from the coast, more than 11,000 structures and 85,000 people will see stormwater flooding in 2070, according to the new figures.
At an event announcing the report today, Mayor Martin Walsh pointed to a map that showed his old neighborhood of Savin Hill in Dorchester underwater in a future flood scenario.
“Climate change affects every aspect of Boston's life,” he said. “This is a roadmap that's going help our city prepare for climate change."
The report also proposes solutions, or “climate resilience initiatives,” but does not provide cost estimates for them. Many would be significant undertakings, such as retooling the city's zoning laws and building code, or retrofitting thousands of existing buildings that may some day find themselves in a floodplain expanded by climate change. Walsh suggested that could include elevating homes in some neighborhoods.
Austin Blackmon, Boston's chief of environment, energy and open space, said the city is launching a feasibility study for a barrier that would close off all or part of Boston Harbor. Blackmon said that would cost $10 billion to $15 billion, however, and could create more problems than it solves by interrupting shipping or ruining coastal ecosystems.
Rather than a costly marine barrier that would defend the entire city from coastal flooding, the report suggests focusing on certain flood pathways in high-risk areas including North Charlestown, Dorchester Bay, and Porzio Park in East Boston.
Other strategies for climate-proofing Boston listed in the report include temporary flood barriers and green buffer zones along the shoreline, dual-purpose “protective and floodable waterfront parks,” and a network of local electrical grids designed to keep running during major storms.
Fulfilling the recommendations of the Climate Ready Boston report would constitute an overhaul of urban infrastructure on a scale seldom seen in American cities except after natural disasters. Boston has endured 21 federal or state-declared disasters since 1991, but none has served as the wake-up call that Hurricane Katrina was for New Orleans in 2005, or Hurricane Sandy for New York in 2012.
But the report points out that if Hurricane Sandy had come during Boston's high tide, just over five hours earlier, the storm surge could have devastated parts of every coastal neighborhood in the city. Instead Bostonians barely felt the hurricane that killed dozens and caused roughly $19 billion in damage in New York. Under future scenarios of sea-level rise, the report's projections show, they would not have been so lucky.
Bud Ris, senior advisor at the Barr Foundation, said local developers are getting the message.
“I've seen a sea change in the past year,” said Ris, who is also a member of a coalition of local businesspeople called the Green Ribbon Commission, one of the reports' co-authors. “Many of the real estate groups here had properties in New York during Sandy. They get it.”
Ris and Blackmon both suggested special taxing districts as a way to pay for investments in climate infrastructure. So-called “business improvement districts” or “district improvement financing” could leverage private money for climate resilience projects to benefit the public, Ris said.
Mayor Walsh said if 30 years ago the city had planned its waterfront with climate change in mind, it would look very different today.
“If we really thought it through we could have done some really spectacular things,” he said. “We missed that opportunity.”