Wave vs. glacier: Slow pace of resiliency plans will leave Downtown at risk for many years to come

More than five and a half years after Sandy devastated Lower Manhattan the city still has no idea how to fund its massive Downtown storm-protection project known as Manhattan Tip meant to wrap the Downtown waterfront with elaborate infrastructure to mitigate catastrophic storm surges.

BY SYDNEY PEREIRA

Nearly six years after Hurricane Sandy devastated swathes of Lower Manhattan, doing billions of dollars in damage, Downtown is no better protected from the next superstorm than it was the day after according to city officials tasked with disaster preparedness.

And the situation isn’t going to improve anytime soon, according to the latest update Community Board 1 got from city agencies in charge of disaster response and resiliency efforts.

Reps from the Mayor’s Office of Recovery and Resiliency and Office of Emergency Management outlined plans for short-term and long-term fixes aimed at protecting Lower Manhattan from floods and storm surges, and the upshot was that nothing is going to happen soon.

The short-term fixes — temporary barriers to hold back flood waters — won’t even be in place until 2019, seven years after Sandy. And the more ambitious long-term adaptations of Downtown’s landscape and infrastructure to better resist flooding are barely even on the drawing board, much less in the budget.

Members of CB1’s resiliency sub-committee, formed back in January is hoping to educate Downtowners about the looming impact climate change will have on their community and press the city for answers about future preparations, were underwhelmed by what city officials offered as an update.

Hesco barriers are semi-permanent structures fabric-lined wire mesh filled with sand which are meant to stand for five years.
Mayor’s Office of Recovery and Resiliency

The short-term measures would include a line of barriers running along South Street from Wall Street to Catherine Slip, according to Emergency Management’s design. Two types of barriers — Hesco barriers and Tiger Dams — would be installed. Hesco barriers are wire mesh containers around four-feet high lined with fabric and  filled with sand, designed to stand for five years after installation. Tiger Dams are more temporary barriers — large, water-filled tubes that would be deployed within a few days of an incoming storm, once an incoming storm reaches tropical storm force winds of 39 miles-per-hour.

As of now, 11 sites are operational around the city with these barriers or similar ones, including a site in Red Hook. But the Seaport won’t see any Hesco barriers until the 2019 storm season, starting around August 1 that year. One reason for the delay, according a city official, is the complex web of interests there that have to be reconciled before any plans can be finalized.

“It takes a considerable amount of review from various agencies and various stakeholders,” said Suzan Rosen, mitigation program manager in the city’s Office of Emergency Management.

Tiger Dams are sturdy tubes that can be quickly unfurled as needed and filled with water to create an instant barrier against storm surges.
Mayor’s Office of Recovery and Resiliency

The Seaport is an interesting site in particular, she said, because of its place as a tourist attraction. There is more traffic, businesses, developments, museums — not to mention residents — forming a host of stakeholders who have concerns about the barriers.

“It is such a large concept that we have to take into consideration so many more of these stakeholders,” added Rosen. Not to mention, the Seaport barrier is the longest installation planned under the Interim Flood Protection Measures program, she said.

The temporary barriers are meant a relatively inexpensive stop gap measure until more permanent, long-term, and expensive solutions can be designed and funded. Hesco barriers cost around $200 per linear foot, and Tiger Dams are around $100 per linear foot, though the latter can vary because they are made in various lengths and diameters, according to Rosen.

The long term study found that over the next 80 years, 11 percent of buildings in Lower Manhattan overall will be at increased risk of monthly tidal inundation, which amounts to some $4 billion worth of properties at risk. Considering the Financial District alone, the percentage of at-risk buildings nearly triples.

At the April CB1 meeting, Justin Schultz of HR&A, the real estate consulting firm that conducted the study for city, also brought up a lesser-known risk known as groundwater table rise. As sea levels rise, saltwater beneath the ground pushes up the fresh groundwater table under the land. As the water table rises, the ground will become less stable, which is expected to destabilize buildings and underground infrastructure. The saltwater intrusion that causes the groundwater table to rise is somewhat like flooding from below — but with no rainfall required. The study estimates the 167 buildings in Lower Manhattan will be vulnerable to such destabilization by 2100, and 39 percent of underground utilities will be impacted — not least our vital subway lines.

Proposals to deal with such longer-term risks range from the rather fatalistic strategy of flood-proofing buildings by sealing off their foundations or elevate their vital infrastructure above the inevitable inundations — and even elevating street’s and sidewalks — to more ambitiously compressive protects such as surge-proof seawalls to keep whole areas dry, and deep-reaching “seepage barriers” stretching all the way down to the bedrock to keep rising seal levels fro pushing up the inland water table.

The resiliency studies these planning experts presented to CB1 nearly six years after Hurricane Sandy were unable to determine what combination of approaches and mitigation would work best for Lower Manhattan, or what such a massive and comprehensive long-term resiliency infrastructure might cost. But it’s obvious to even a casual observer that, whatever the cost, the money simply isn’t there.

The city’s post-Sandy drive to storm-proof Downtown — the Manhattan Tip Lower Manhattan Coastal Resiliency project — finally received $108 million in funding in 2015, and the city doesn’t seem to have a clue where the rest of the money will come from.

The long-suffering leadership of CB1 has learned to be sanguine about the slow pace of resiliency policy, with board chairman Anthony Notaro acknowledging the obvious point that the money is “going to have to come from a combination of different places,” but also expressing the resolute confidence of a civic leader who has persevered through not only Sandy, but also 9/11.

“We have solved many difficult problems in the past, and I believe we’re up to this task,” said Notaro. “But it will take time, money and teamwork.

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One Response to Wave vs. glacier: Slow pace of resiliency plans will leave Downtown at risk for many years to come

  1. The Metro NY-NJ Storm Surge Working Group advocates for a “layered defense” system encompassing both an off-shore regional barrier system and a network of on-shore perimeter defenses that would be developed by NY City plus participating coastal communities surrounding the 1,000 miles of shoreline of NY Harbor, its tributaries and the lower Hudson River.

    Such a layered defense strategy specifically separates the functions of the mighty regional offshore barriers, designed to block occasional dangerous storm surges from future megastorms, from the manageable low seawalls needed to hold back slow but insidious rise in global sea level.

    Regional storm surge barriers must be held open 99.99% of the time for the purposes of efficient navigation, fish migration, and to allow freely-flowing tidal currents, river discharges to the ocean and daily harbor flushing. But there is no way regional storm surge barriers can hold back sea level rise; only perimeter seawalls can do that.

    A robust, regional offshore barrier system, designed specifically to withstand the worst storm surges that nature can hurl at us, enables the City and other coastal communities in both NY and NJ to focus their attention on erecting modestly-low level seawalls, abutments and barrier beach re-nourishment projects in a grand City and bi-state partnership.

    Only in this way can the essential tasks of protection against both storm surges and sea level rise be separated and accommodated in an advantageous cost/benefit scenario. The large plus will be the gain in support of both Metropolitan and harbor-fringing cities such as Hoboken, Port Elizabeth, Jersey City, etc, which will never accept impossible 20-25’ high seawalls which will block their iconic shoreline views and severely restrict access to the waterfront, which in modern times is a salient feature of city life.

    Malcolm Bowman, PhD, Stony Brook University.
    Chair Metro NY-NJ Storm Surge Working Group

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