Floodwalls for Manhattan?

Nearly five years after Hurricane Sandy inundated much of Lower Manhattan with floodwater, causing billions of dollars in damage, city officials are seeking community input on how to best keep downtown streets dry during New York’s next superstorm.

Representatives of the Mayor’s Office of Recovery and Resiliency outlined potential steps the city could take to combat storm surge at three of Lower Manhattan’s most vulnerable locations at a May 18 community meeting at St. Paul’s Chapel. The session focused on various options for new flood mitigation infrastructure that could be installed in the South Street Seaport area, near Pier A and the Battery, and in the northern area of Battery Park City near Stuyvesant High School.

The public workshop was part of the community engagement phase of the Lower Manhattan Coastal Resiliency project, part of the city’s $20 billion OneNYC resiliency program aimed at mitigating the impact of rising sea levels and severe storms, which are expected to increase in frequency in the next century. More than $100 million in city capital funding has been dedicated to improving infrastructure in Lower Manhattan, which is particularly vulnerable to flooding due to a number of low-lying waterfront areas. The problem of flooding is expected to worsen in the decades to come — by the 2050s, city officials say, sea levels are likely to rise one to two feet; by 2100, levels could rise by as many as three to six feet.

Low elevations made the northern and southern ends of Battery Park City significant breach points for storm surge waters during Hurricane Sandy; much of West Street was flooded in the area by waters flowing from near Stuyvesant High School and Pier A. Planners outlined several measures that could be installed to protect crucial infrastructure in the area, such as subway lines, the Battery tunnel and various utilities. Near the Battery, planners said, a raised berm, potentially rising as high as ten feet above the surrounding terrain, could be installed between the sidewalk and the park area to hold back water during a flood. A bike path could be installed along the top of such a berm. Other infrastructure options were presented as better suited for the waterfront in the northern part of Battery Park City, such as raising the entire esplanade or installing a permanent wall along the street, set back from the waterfront greenway.

The South Street Seaport area poses its own challenges, such as the FDR Drive, where new flood intervention measures would have to be built around existing columns supporting the elevated highway. Planners outlined various types of barriers that could be installed under the highway overpass, including “deployable” walls, which could be stored elsewhere and installed prior to a storm.

The planners urged community members to discuss tradeoffs between the various design concepts. For example, permanent walls would impact access to the waterfront and be negative from an aesthetic perspective, but wouldn’t require the deployment and storage costs that a removable wall would entail.

Conspicuously absent from the meeting, as some community members noted during a question-and-answer session, was any substantive discussion of the costs associated with installing and maintaining the various options presented at the meeting. Officials from the mayor’s office said that the session was intended to gauge community preferences regarding various design choices and that cost analysis would occur later in the process.

The Financial District was not slated for inclusion in the discussion — another repeated point of contention, with several community members expressing disappointment that the city representatives were reluctant to discuss measures to protect one of the city’s most important job centers nearly a year after the Lower Manhattan Coastal Resiliency project launched. Jordan Salinger of the Mayor’s Office of Recovery and Resiliency said that Financial District was omitted from the agenda because the area “needs more work.” “We didn’t want to put something in front of you today that would be a problem long-term,” he said, adding that the neighborhood presents the “biggest challenge” to planners because it presents “limited possibilities” with respect to intervention measures. “The financial district is more challenging, but we will bring that to you as soon as it’s ready,” Salinger said.