“A storm-surge barrier may be appropriate, but it's never one thing that is going to protect you,” says Adam Freed, a program director at the Nature Conservancy in New York, who until late last year was deputy director of the city's office of long-term planning and sustainability. “It's going to be a holistic approach, including a lot of unsexy things like elevating electrical equipment out of the basement and providing more back-up generators.”
As part of that holistic effort, officials are exploring options for expanding the remaining bits of wetlands that once surrounded the city and buffered it from storms. In his address, Bloomberg called wetlands “perhaps the best natural barriers against storms that we have”.
But most of the city's wetlands have become prime real estate in recent decades, and Sandy made clear the consequences of developing those areas, says Marit Larson, director of wetlands and riparian restoration for the New York parks department.
A few weeks after the storm, Larson parks her car near the beach on Staten Island and looks out at a field of Phragmites australis, a common marsh reed. The field is part of Staten Island's 'Bluebelt' program, initiated in the late 1980s to promote wetlands and better manage storm-water runoff. But the patch of wetlands here is smaller than a football pitch, and Sandy's surge rolled over it, damaging the nearby row houses. “If you look at the historical maps,” says Larson, “everything that used to be a wetland got wet.”
Up to code
New York is now moving to strengthen its network of existing wetlands, which cover some 2,300–4,000 hectares. The mayor's budget plan for 2013–17 includes more than $200 million to restore wetlands as part of an effort to protect and redesign coastal developments.
Sandy also showed how proper construction can help to reduce risks from future storms. In one Staten Island neighborhood, a battered roof rests on the ground, marking the spot where an ageing bungalow once stood. Next door, a newer house still stands, with no apparent damage apart from a flooded garage — sturdy proof of the value of modern building codes. In New York, newer buildings constructed in 100-year-flood zones, which are defined by the US Federal Emergency Management Agency (FEMA), cannot have any living spaces or major equipment, such as heating units, below the projected flood level (see 'Danger zone').
The city's zoning provisions could not protect against a storm like Sandy: officials estimate that two-thirds of the homes damaged by the storm were outside the 100-year-flood area. But scientists say that the FEMA flood maps were out of date, so even century-scale storms could cause damage well beyond the designated areas. Last month, FEMA began releasing new flood maps for the New York region that substantially expand this zone.
In their latest study, Emanuel and his colleagues estimate the average annual flood risk for New York as only $59 million to $129 million in direct damages. But costs could reach $5 billion for 100-year storms and $11 billion for 500-year storms. These figures do not include lost productivity or damage to major infrastructure, such as subways.
Bowman and other researchers argue that the city should commit to protecting all areas to a 500-year-flood standard, but not all the solutions are physical. A growing chorus of academics and government officials stress that the city must also bolster its response capacity and shore up the basic social services that help people to rebuild and recover.