By mid-century, nearly 50,000 homes a year in Massachusetts will face a substantial risk of structural damage from flooding, an 11 percent increase from today, according to a report.
As sea levels rise and storms become more powerful as a result of climate change, flooding will pose a serious threat to nearly 4.3 million homes across the country by 2051. That could cause annual losses of more than $32 billion, a 61 percent increase from the estimated costs today, according to an analysis by First Street Foundation, a New York nonprofit research group that specializes in flood risk.
The growing dangers are likely to spur insurance companies to increase their premiums and cost the National Flood Insurance Program, which provides government-backed coverage, billions in additional losses.
“Flood risk brings with it real and potentially devastating financial impacts that aren’t being priced into the market or considered by most Americans,” said Matthew Eby, executive director of First Street Foundation.
In Massachusetts, the financial losses from flooding will probably rise to an estimated $316 million, a 36 percent increase from today, according to the report. The state now ranks sixth in terms of the number of residential properties — those with up to four units — likely to experience structural damage from flooding.
In Boston, where more than 3,000 properties a year will face substantial risk of damage from flooding, those losses are likely to exceed $62 million a year in 30 years, 75 percent more than now.
Those increased risks are apt to send the price of flood insurance soaring. For example, in the city’s newly developed Seaport, one of the nation’s most vulnerable neighborhoods to rising sea levels, the average premium to insure a home from flooding is likely to surge to nearly $20,000, almost 10 times the average cost of premiums today, according to the report.
“The Seaport already faces relatively high premiums, and they will need to get even higher to account for both current and future changes to risk,” said Jeremy Porter, director of research at First Street Foundation.
The government’s flood insurance program, with artificially reduced rates, effectively subsidizes the construction of expensive properties along the water, as taxpayers will ultimately be left with the costs of future flooding, he said.
Last year, a report from First Street Foundation estimated that more than 336,000 properties in Massachusetts are at some risk of flooding, 65 percent more than existing flood maps indicate. That report said that Boston had more than 19,000 homes and businesses at risk of flooding, about 19 percent of existing properties.
The new report focused on a smaller number of properties where floodwaters are likely to seep into the structures and cause lasting damage. “They are not built to standards that protect them against flooding,” Porter said.
State officials said they were reviewing the report, noting they have spent nearly $1 billion on efforts to study and prepare for climate change since 2015.
“The Baker administration ... remains committed to ensuring Massachusetts is prepared for the growing impacts of climate change,” said Craig Gilvarg, a spokesman for the state Executive Office of Energy and Environmental Affairs, in a statement.
Jack Clarke, a member of the state’s Coastal Erosion Commission and a former assistant director of its Coastal Zone Management Program, noted that Massachusetts, particularly, will be more vulnerable to flooding in coming years, as 85 percent of the population lives within 50 miles of the coast.
Climate models suggest seas could rise as much as 10 feet by the end of the century, with increasingly powerful storms bringing substantially more precipitation and flooding to Massachusetts.
“This is another wakeup call to state, federal, and local decision-makers to stop encouraging, permitting, and subsidizing development in areas like Boston’s Seaport, or what I refer to as the Inundation District,” Clarke said.
After Boston, Lowell is likely to have the state’s second-highest financial losses from flooding, at nearly $16 million, or 7 percent more than today, according to the report. Gloucester is apt to rank third in annual economic losses, at an estimated $12 million, up 23 percent from today.
In West Yarmouth on Cape Cod, annual financial losses are likely to rise by 114 percent to $1.2 million; Salem’s are projected to increase by 94 percent to nearly $4 million; and in Chelsea, costs could grow by 84 percent to nearly $1 million, according to the report.
Environmental advocates said the report underscores the need to minimize flood risks, such as by protecting and restoring river floodplains and ensuring there are sufficient undeveloped areas to absorb stormwater.
“The challenge in Massachusetts is that so much of our state is already developed, and those flood-prone areas often mean a nice river or ocean view,” said Julia Blatt, executive director of the Massachusetts Rivers Alliance. “Whatever else we do, neither our government nor private insurers should be paying anyone to rebuild in a flood-prone area.”
Deb Markowitz, state director of the Nature Conservancy, said the report makes it clear that state and federal officials need to update flood-risk maps and insurance models and encourage policies that promote a managed retreat from coastal areas.
“The Commonwealth must take an all-hands-on-deck approach,” she said. “There is nothing worse than throwing good money after bad. This report is a stark reminder that, unless we change the way we manage risk, we will keep paying to rebuild at-risk properties, over and over, ultimately bankrupting the systems that are there to help protect us.”
The report suggests that either insurance rates will rise in the coming years or taxpayers will bear a greater share of the costs. The National Flood Insurance Program, which has paid tens of billions of dollars to cover claims since Congress established it in 1968, will probably have to increase premiums by nearly five times to cover its risks, the report said.
Properties in Boston, for example, pay an average of less than $700 a year for flood insurance; in 30 years, the average cost of repairing a flooded property is likely to exceed $9,000, according to the report. The disparity in rates and likely costs is similarly high in other municipalities, including Lowell, Haverhill, and Methuen.
Tom O’Shea, director of natural resources at the Trustees of Reservations, which owns more coastal land than any other property owner in the state, called on the Baker administration to provide relief to property owners and residents who may not be able to afford higher insurance rates.
“We must work together,” he said. “Flooding knows no community or property boundaries.”