NewsApril 10, 2012

Climate Change Could Cripple New York's Transportation

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Andrew Freedman

By Andrew Freedman

When arriving at La Guardia Airport in New York, it’s easy to see the stark realities it faces in trying to cope with global warming. As jets glide in over the brackish waters of Flushing Bay, one can almost reach out and touch the water as it laps against the small levees at runway’s edge.

By mid-century, global warming-related sea level rise is expected to render these levees ineffective against even relatively weak storms, according to a 2011 climate assessment and supported by Climate Central’s report on coastal flooding. And the predicament facing La Guardia is far from unique. All three of the city’s major airports are situated along the ocean and face similar sea level rise-related risks.

The flooding likely to occur in the greater New York City area as a result of a 4-foot rise in sea level. Areas that are no longer white, including La Guardia Airport, represent those underwater. Credit: Surging Seas/Climate Central.

But it’s not just the city’s airports at risk. As 106 million passengers per year funnel through the terminals, collecting their luggage, they’ll head into New York via taxis, trains, cars and buses – another network of transportation that is at considerable risk of flooding from the combination of sea level rise and storm surges.

As sea level increases in response to manmade global warming, the 100-year storm is turning into a far more common event, and climate change adaptation is taking on a heightened sense of urgency throughout the transportation sector. The challenges are particularly acute in the New York City area, where mass transit moves more than 8 million people every day, 24/7, into and out of a city with 520 miles of waterfront.

Given the climate change-related challenges the city faces, it’s no surprise New York is mobilizing to fortify its infrastructure. It is spending $1.5 billion over 15 years to improve its stormwater management, cooling white roofs and clean-fuel buses, and has pledged to reduce city-wide greenhouse gas emissions below 2005 levels by 2030.

Officials are studying various coastal protection strategies, from “wave attenuators” that can disperse the energy from incoming swells to storm-surge barriers. As David Bragdon, director of the mayor’s Office of Long-Term Planning and Sustainability told the New York City Council in December, “Our densely populated city does not have the option of picking up and moving to higher ground.”

While New York gets a lot of credit for its efforts, some say the city, state agencies and private companies are not moving fast enough to keep pace with updated scientific projections.

Klaus Jacob, a senior research scientist at the Lamont-Doherty Earth Observatory at Columbia University and the lead author of a state-sponsored report that examined the climate change-related exposure of New York’s transportation infrastructure, warns of rapidly increasing vulnerabilities facing the metro area.

Aerial view of La Guardia Aiport. Credit: PhillipC/flickr

“What really surprised us was that there is already considerable risk,” Jacob said. Regarding LaGuardia Airport, Jacob says raising the existing levees much higher may not be a viable flood-protection option.

“. . . After all, aircraft can’t jump over those when they take off and during landing.”

Jacob is pessimistic that sufficient resources are being devoted to climate adaptation efforts within transportation agencies, such as the Metropolitan Transit Authority (MTA), which is a state agency.

“The transportation agencies are now facing the reality that it will cost money, and that’s why nothing is going to happen,” he said.

To understand Jacob’s pessimism, one need only consider the growing risk exposure of the cash-strapped New York City subway system.

The MTA provides nearly 8.5 million passenger trips per day via 600 miles of track, to about 500 stations, using more than 6,000 trains worth about $11 billion. Throughout the subway system, there are nearly 300 pump stations, 200 fan plants, and more than 200 electric substations. Such infrastructure does not come cheaply — the MTA’s assets have a combined value of $22 billion.


That elaborate system of pumping stations keeps water out of the subway tunnels, which are vulnerable to flooding from heavy rainfall or storm surge in many locations. Floodwaters can enter subway tunnels through ventilation grates in the streets above, and through station and tunnel entrances.

Computer simulations indicate that many of the tunnels in Lower Manhattan can flood completely in as little as 40 minutes under certain conditions.

According to the assessment that Jacob led, the MTA’s assets — including trains, stations, and electrical equipment — are at “severe” risk of damage from a combination of sea level rise and storm surge-related flooding.

This was also supported by Climate Central’s own scientific research published in March, which showed that during the next several decades, the frequency of damaging storm surges in places like New York will rise significantly as sea levels creep up. The research projected a sea level rise of 13 inches in New York by 2050, and found that global warming-related sea level rise more than triples the odds of a 100-year flood or worse by 2030.

Without global warming, the odds of such a flood would be just 8 percent by 2030, but with global warming the odds rise to 26 percent.

In addition, the funnel shape of New York Harbor has the potential to magnify storm surges already supplemented by sea level rise, threatening widespread areas of New York City.

Even without sea level rise, a 100-year flood would inundate large portions of the subway system, Jacob’s team concluded. But with a 4-foot rise in sea level, storm-related flooding would inundate much of Manhattan’s subways, including almost all of the tunnels crossing into the Bronx beneath the Harlem River and the tunnels under the East River. Five of the city’s subway lines have extremely low points of entry to tunnels, subways, or ventilation shafts: they are less than 8 feet above sea level.

Although Jacob’s team used a 100-year flood definition that differed from Climate Central’s, both analyses came to the same, disturbing conclusion: New York is at increasing risk of coastal flooding from a combination of storms and sea level rise.

100-year storm surge flooding of Lower Manhattan subways and adjacent East River tunnels crossing to Brooklyn in a scenario that includes 2 feet of sea level rise. Heavy blue lines indicate fully flooded tunnels. Background colors show topographic surface elevations (yellow≥30ft). Credit: ClimAID Report. Click on image for a larger version.

According to Projjal Dutta, MTA’s director of sustainability initiatives, another key vulnerability is the tendency for subway tunnels to turn into the “sewer system of last resort” during heavy rainstorms, as water pours into the system faster than it can be pumped out. “The intensity of precipitation is what basically kills us,” Dutta said.

The rule of thumb, according to a city official, is that every inch of rain that falls in the city means there are a billion gallons of stormwater runoff to deal with.

A heavy rainstorm in August 2007, during which up to 3.5 inches of rain fell in just two hours, shut down 19 major segments of the subway system, affecting 2 million passengers.

In the wake of that event, the MTA spent millions to limit the ability of water to pour into the tunnels in the affected areas by raising ventilation grates above the sidewalk level, paving over other grates, and installing water-activated closing devices. But the MTA cannot take similar actions throughout its system, largely because the costs of these measures – $33.6 million in this specific instance – would divert too much money away from other necessary capital projects. That money could have bought the MTA about 20 new subway cars, for example.

Heavy precipitation events are already becoming more common due in part to global warming, a trend that is expected to worsen in coming years, according to a recent report from the U.N. Intergovernmental Panel on Climate Change.

The possibility that a single storm could incapacitate the subway system was driven home to New Yorkers last year when the subway was shut down for the first time in history ahead of Tropical Storm Irene. Despite the storm’s weakened state when it arrived in New York, as well as extensive efforts by the MTA to protect the tunnels, water still came within inches of flooding parts of the subway system in Lower Manhattan, according to Dutta.

A key question facing planners is how quickly storms with Irene-like impacts will transition from being one-in-50-year events to events that recur every 10 to 20 years. Most scientists expect this transition to take place as the climate warms, but there are uncertainties concerning the timing. Such details make a huge difference when weighing the costs and benefits of different climate adaptation options.

Prior to Irene, the last storm with Irene-level coastal impacts in New York City occurred in December 1992, a 20-year separation.

For Irene, Dutta said, “We took measures that we can’t take every other year.”

New York City subway's closed in preparation for Hurricane Irene, August 2011. Credit: ccho/flickr

Dutta says climate change factors need to be incorporated into regular transportation planning procedures. Right now, that isn’t the case. Instead, climate concerns are tacked on to other plans. For example, if a subway station is due for repairs, engineers may add measures related to climate adaptation into the work orders, such as by raising rails by several inches.

“You hope hard as hell that those 8 or 9 inches buys you some time, and the water stops rising within that time,” Dutta said.

Mainstreaming climate adaptation into city planning is a key goal of the New York City Climate Change Adaptation Task Force, which is scheduled to unveil a set of recommendations on maintenance and capital improvement programs later this year. The city is working toward determining what they think is an acceptable level of climate risk, rather than spending billions to guard against every possible climate change scenario.

“There are a lot of assessments out there that are based on the maximum of maximums, worst-case scenario, [and] we really need to look at the full context of the issues we’re dealing with,” said Adam Freed, deputy director of the New York City Mayor’s Office of Long-Term Planning and Sustainability.

A key factor holding back agencies like MTA is that the money for such work currently comes out of the same pot as other capital improvement projects. At a time when state budgets are being cut, this severely weakens the MTA’s ability to pursue large-scale adaptation projects.

Even with more funding, transportation planners and city managers still face an uphill challenge in grappling with climate change.

As Freed put it, “You’re never going to have anyplace in the world that is climate-proof.”

New York is doing far more than most cities to adapt to climate change. But because the city is so big and so critical to the country and the world as an economic engine, climate change-related disruptions would have particularly huge impacts in and outside of New York. The reality is that the city, like others in the U.S. and around the world, would benefit from more resources and political capital devoted to climate change adaptation and mitigation efforts, rather than borrowing money from other priorities, like the MTA is doing.

Otherwise, there is a real possibility that officials will accept too much climate change-related risk when planning for the future. And that may prove exceedingly costly in the years to come.