Dutch global water management expert Piet Dircke has some good advice on how New York City can prepare itself for another hurricane – and building a seawall is not the answer.
Dircke, who has designed flood protection plans for New Orleans, Jakarta, Rotterdam and Amsterdam, met with Mayor Bloomberg and former Vice President Al Gore last week in Manhattan after the mayor laid out a plan for the city to combat climate change.
“We know there are floods, we know there is a risk, but we don’t know what the solution looks like,” said Dircke, who works for engineering firm Arcadis and is an expert on climate adaptation and Delta cities, such as New York.
In 2009, Dircke designed a conceptual barrier to be placed in the Verrazano Narrows, for a conference run by Stony Brook University professors who wanted to work out solutions for the city’s flooding problems.
“It has to be barred over a complete system, a Delta Plan. We would have to call it the Hudson Plan or Flood Protection Plan for New York,” Dircke explained. “It would consist of barriers as well as levies and the restoration of marshlands, wetlands and coastal protection of floods.”
The barrier system would work as follows. The two doors in the middle, called sector gates, are required because New York is a port city.
“We don’t want to seal off New York Harbor. We want it to keep it open for shipping,” he said. “The Hudson Bay is a tidal estuary with very strong tides going through the narrow opening to keep this in-and-out flow at the level that it is now. A consecutive number of big doors and lifting gates resembles barriers in the Netherlands, especially Rotterdam. In storm conditions, the doors are closed to keep the hurricane outside.”
The estimated cost of the structure is around $6 billion, but due to the expanse of the city’s waterways, Dircke said at least three barriers would be needed: one at Arthur Kill, one at the East River and one at the Verrazano Narrows. That would cost about $10 to $15 billion.
“Some people even consider a big outer barrier from Sandy Hook to Rockaway Point. But you need a system, which is not barriers only,” Dircke explained. “You need levies, dunes and building codes.”
Dircke does not recommend a barrier system to protect the city. He thinks a focus plan – similar to what Bloomberg is proposing – is the way to go.
“A good plan that simply tells us what the scenarios are. What does the city look like? Will the sea level rise? What can we expect?” Dircke said. “Then we ask, how do we want to defend ourselves? Do we keep it [water] out? How much emphasis on technical or natural solutions? How much do we want to invest?
“New York is ready for an integrated plan,” he went on. “Maybe we don’t build those barriers immediately. We can start by having other options on the table. Secondly, New York has shown after Sandy that it can recover pretty quickly. Subways cannot be sealed off with sandbags, but with advanced systems.”
Dircke said that the most vulnerable buildings in the city, especially in Lower Manhattan, can be made water resilient. He also suggested protecting the city’s telecommunication and transportation networks in a more efficient way.
“New York has a lot of options. It seems like a big city in distress but…New York is built on solid ground and is not sinking into the ocean,” Dircke said. “Organic and urban measures can be considered before we build barriers. I am positive and optimistic about New York.”
In the same vein, the Metropolitan Waterfront Alliance released a 12-point plan to both revitalize the waterfront and protect the city from future storms.
That plan includes: maintaining the commitment to revitalizing the waterfront; weighing the benefits of sea gates and barriers; expanding maritime infrastructure; updating FEMA flood maps; creating government waterfront oversight; retrofitting existing waterfront infrastructure; restoring the regional waterfront to mitigate future flooding; adopting neighborhood-based climate change planning strategies; considering retreat from land that is high-risk; securing hazardous materials and contaminated areas; creating and funding sufficient government budgets to protect the waterfront and reviewing zoning codes and standards to prevent loss of life.
“Resiliency and a great waterfront go together,” said Roland Lewis, MWA’s CEO. “We must agree to protect both the shoreline and protect our vital access to it.”