USA: Coastal cities race to keep tabs on rising seas, skyrocketing costs

Climate Liability News

By Dana Drugmand

Major coastal cities—from New York and Boston to San Francisco and smaller communities like Imperial Beach, Calif.—are already preparing for a potentially perilous future because of sea level rise.

But even though these cities have spent years assessing their risks, and found price tags that run into the billions to adapt, new studies of Antarctic ice loss and coastal real estate risk suggest they may be far underestimating the costs that lie ahead.

A recent study published in the journal Nature found that the rate of Antarctic ice loss has tripled in the past five years. That means sea level rise could sink more than 300,000 U.S. coastal residential and commercial properties(worth approximately $117.5 billion) by 2045, according to an analysis also published recently by the Union of Concerned Scientists.

It left open the major question of how cities can keep their risk assessments in line with science as it continually develops. Several of these cities are suing fossil fuel companies to help pay for climate adaptation because that price tag keeps getting higher.

“The costs of adaptation are currently estimated in the billions of dollars, which is why we are seeking to recover damages from the defendants whose products caused harm to New York City,” said Dan Zarrilli, chief resilience officer for the New York City mayor’s office.

New York City filed a public nuisance lawsuit against the five largest oil companies in January and awaits a federal judge’s ruling on the oil companies’ motion to dismiss.

According to the UCS report, New York ranks third in the nation for most homes at risk by the end of the century. The report’s high sea level rise scenario projects an average of 1.9 feet of sea level rise for New York by 2045 and 7 feet by 2100.

Zarrilli said the city continually evaluates new information as sea level rise science continuously evolves.

“Since 2010, New York City has relied on the best available science as developed and peer-reviewed by the New York City Panel on Climate Change, which continues to assess new climate projections,” he said. “All of the City’s resiliency investments take into account this evolving science and are being planned for continued adaptation as projections may change.”

Climate Liability News reached out to several other coastal cities’ representatives to find out how they are preparing for sea level rise and handling new data and changing projections.


At a recent International Mayors Climate Summit in Boston, Mayor Marty Walsh spoke of the “huge challenge” of sea level rise and mentioned several of the city’s resiliency initiatives. “Sea level rise is adding to the urgency here in Boston,” he said.

“The city conducted its own vulnerability assessment in 2016 and is committed to updating it as science evolves,” said Lauren Zingarelli, director of communications in the Mayor’s Office of Environment, Energy, and Open Space. “We’re currently focused on protecting those neighborhoods most at-risk to future sea-level rise, such as building a deployable floodwall across one of the parks in East Boston.”

Currently, the city is using a projection of 40 inches of sea level rise in the medium to long term.

Boston’s climate resiliency and adaptation initiative, called Climate Ready Boston, includes a process to continuously review the best available climate science. A team of regional climate scientists—the Boston Research Advisory Group (BRAG)—has developed a Climate Projection Consensus report. It details the city’s vulnerability to four climate impacts: extreme temperatures, sea level rise, extreme precipitation and coastal storms. BRAG said it reviews the most recent available data on climate change and borrows emissions scenarios from the Intergovernmental Panel on Climate Change.

“We plan to reconvene this group every five years to look at the most updated science and reports, and then re-submit the report to the city and see if there’s any changes that the city needs to be making to those projections in the short or long term,” said Mia Mansfield, Climate Ready’s  program manager.

Mansfield said that building developers in vulnerable areas are required to include an extra 1 or 2 feet elevation to account for potential higher sea level. “We’re adding in a level of extra safety and extra buffer,” she said, adding that the 40-inch prediction “is a likely scenario that we can anticipate across the different carbon emissions pathways.”

This may not be the number the city always uses in the future, but it is the best estimate for now to inform adaptation planning. “As the science continues to change we’ll reconvene our scientific advisory group and reassess,” Mansfield said.

While the city does not have a total cost for sea level rise adaptation, it has estimated the costs of neighborhood-specific projects. The deployable sea wall in East Boston is expected to cost $100,000. Elevating main streets in Charlestown is projected to cost $2-3 million.

“It’s going to be expensive, but you have to counter that by looking at the benefits of doing this work, the avoided losses and the investments that can be made into neighborhoods at the same time,” Mansfield said.

Imperial Beach

Situated on the southern tip of San Diego Bay and about 11 miles south of San Diego, the city of Imperial Beach is already experiencing flooding and coastal erosion. The city is surrounded by water on three sides, making it especially vulnerable as sea level rises. The city’s vulnerability analysis has a high-end sea level rise scenario of 6.5 feet by 2100.

The city was one of the first group of California cities to file a suit in state court against the fossil fuel industry to pay for damages related to climate change. It joined with San Mateo and Marin counties to sue 37 fossil fuel companies last year. The latest ruling in the case, keeping it in state court, is currently being appealed by the companies.

Mayor Serge Dedina said the city has projected adaptation costs on the beachfront side alone will surpass $100 million, and he expects them to keep rising.

Dedina said he is aware of the recent NASA study on Antarctic ice loss and keeps abreast of developments in sea level rise science to guide policy efforts. He said the city’s Local Coastal Plan—a state-mandated policy document for coastal planning that includes sea level rise responses—is currently being updated.

According to Dedina, the city’s sea level rise response planning “is already in high gear.” It has worked with other vulnerable coastal cities to develop resilient infrastructure projects. It is also seeking a permit from the Army Corps of Engineers for emergency beach replenishment.

“We’re being diligent and taking steps to be prepared, but we recognize that protecting our city will also require regional solutions that aren’t yet in place,”  Dedina said.

“The most expensive responsive measures undertaken in Imperial Beach so far are large beach nourishment projects undertaken by other agencies, including the State of California,” Dedina said. “Costs to Imperial Beach will increase as its responsive measures get underway.”

San Francisco

Climate adaptation and sea level rise planning is also well underway in the San Francisco Bay Area—a coastal area highly vulnerable to climate impacts and a hotspot for climate liability lawsuits. In addition to the counties of Marin and San Mateo, the cities of Oakland, Richmond, and San Francisco have sued fossil fuel companies seeking compensation for climate impacts. The Oakland and San Francisco lawsuits were recently dismissed by a federal judge and the cities have not yet announced whether they will appeal.

The municipal planners, however, can’t wait for resolution to the lawsuit and are preparing for sea level rise adaptation. Maggie Wenger of the San Francisco Planning Department oversaw the city’s Local Coastal Program amendment, and as with Imperial Beach, San Francisco’s LCP specifically addresses coastal erosion and sea level rise.

Wegner said the city is currently projecting up to 6 feet of sea level rise, plus another 3.5 feet in the case of an extreme flood event.

“The 2018 update to the state’s SLR Guidance includes unlikely but much more extreme scenarios, including accelerating Antarctic ice loss,” Wenger said. “The city is beginning the process of incorporating the new guidance (up to 10 feet of SLR in 2100) in our mapping and planning processes.”

She said there is no official cost estimate for sea level rise adaptation right now. “We are still in the process of assessing our vulnerability to sea level rise impacts and what consequences those vulnerabilities have for people, the environment and the economy. Adapting to sea level rise and other climate impacts will be an ongoing process and will likely include actions taken by the city, private investors, and regional, state and federal government. These factors all make it difficult to estimate a total cost for adaptation.”

Wenger said the city is just beginning to wrestle with how to plan for a worst-case scenario for sea level rise. “Our adaptation planning efforts have always studied a broad range of possible futures but that range may need to expand even more,” she said. “We have also emphasized the need to build adaptive capacity into projects so if we are facing extreme sea level rise, we can retrofit or improve infrastructure accordingly.”

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