Tuesday, July 30, 2013

Two Possible NYC Responses to Rising Water Levels

Subway stop after Sandy, October 29, 2013.
Robert Trentlyon has been keeping his friends informed about rising water levels and what they might mean for New York City. Here are two responses to the problem that have appeared recently. My thanks to him for sending them to me.

Response #1. A NYC Plan to Allow Flooding (by Douglas Hill)

New York City plans to be flooded. Unlike people living in several cities in Europe and New England who are protected from coastal flooding with storm surge barriers, New Yorkers are promised only “resilience,” the ability to withstand and recover. Because New Yorkers are tough. So says Mayor Bloomberg’s new plan for the city, A Stronger, More Resilient New York.

Storm surge, a gradual rise in sea level over a few hours or days, is identified in the Mayor’s plan as the most severe threat from climate change, worsening by the 1950s as sea level rises and hurricanes become more severe. Two or three storm surge barriers that would be closed to block the entrances to New York Harbor when a storm surge approached would protect the entire inner city as well as nearby New Jersey and the Hudson Valley, places that are blank areas on the City’s flood maps.

Instead, the Mayor’s plan calls for a patchwork of local measures to protect the most vulnerable areas in the inner city, including Red Hook in Brooklyn, Southern Manhattan, the lower East Side, East Harlem and Hunts Point in the Bronx. These would be guarded not with conventional seawalls or levees but with a novel “integrated flood protection system.” Exactly what that means would be determined by a global design competition.

What the planners seem not to have noticed is the findings of the Interagency Performance Evaluation Task Force (IPET), a monumental study of the lessons of Hurricane Katrina in New Orleans in 2005. Where the floodwalls failed in New Orleans was at their ends, either at the junction with another type of structure or adjacent land. Thus, these fragmented protection measures in the City may well be outflanked by flood waters, and they almost guarantee that nearby neighborhoods would suffer worse flooding.

Resilience would otherwise be provided by individual owners of buildings or homes who would be expected to move their utilities and furnaces out of the basement into upper floors, or in some cases to raise their entire houses above the expected flood level. Whatever the merits of some of these local plans for interim protection, the City needs long-term protection as the threat of coastal flooding worsens, a concept that seems missing from the Mayor’s plan.

Conceptual designs and cost estimates for barriers to protect New York City were presented by four major engineering firms in 2009 at a conference sponsored by the Metropolitan Section of the American Society of Civil Engineers. Similar barriers have been built during the past 50 years and have successfully protected London, Rotterdam, and St. Petersburg in Europe, and New Bedford, Providence, and Stamford in New England. At another ASCE conference in April, the five organizations that provide the metropolitan region with power, transportation and wastewater treatment detailed the myriad individual damages due to the storm surge from Superstorm Sandy, and agreed with the conclusion of the Port Authority that “an increased regional approach may be required to provide a better response.”

Why not storm surge barriers? One of the 445 pages of the Mayor’s plan is devoted to dismissing storm surge barriers for New York City.

Cost? The Mayor’s plan estimates the cost of barriers as $20 to $30 billion. By comparison, the City’s proposed Phase 1 is estimated at $20 billion, with more to come. The cost of Sandy to New York City alone is estimated at $19 billion. By the 2050s, a Sandy would cost the city $50 billion, according to the Mayor.

Social justice? The barriers would create an “insiders/outsiders dynamic,” according to the Mayor’s plan, where those behind the barriers would receive maximum protection, and others would be left out.

But apparently the Mayor ‘s fragmented plan , where neighborhoods judged to be vulnerable are given local protection at the expense of nearby neighborhoods, would not.

Hydrodynamic and environmental impacts? Well, they haven’t prevented other cities from being protected, but all the more reason to begin to evaluate what these impacts may be and how they may be ameliorated.

Safety? Although none of the several other barriers elsewhere has ever failed, in some cases for half a century, it is feared that their failure in New York would lead to catastrophic flooding. But no surprises. Better, it would seem, for New York City just to plan to be flooded.

Douglas Hill, EngScD, P.E., F.ASCE is a consulting engineer and adjunct lecturer at the School of Marine and Atmospheric Sciences at Stony Brook University.  Address: 15 Anthony Court, Huntington, NY 11743. 631-421-5544 dhill19@optonline.net or Douglas.Hill@StonyBrook.edu.

Response #2. Layered Strategy. The following was posted by Joe Trezza on the Staten Island Advance site, July 27, 2013:

Political and scientific leaders recently made their own waves as they debated plans for post-Sandy protection aboard a luxury yacht touring New York Harbor. Professional opinions differed between a representative of the mayor's office and a leading engineer who took the floor on the top deck of the Zephyr, which left South Street Seaport in Manhattan on a two-hour trip sponsored by the Working Harbor Committee that included much of Staten Island's North and West shores.

The tour was called "Beyond Sandy," and for paying customers, it brought together top minds to debate the best ways the city can brace itself for future storms.

William Haas, senior policy advisor to Mayor Bloomberg's Special Initiative for Rebuilding and Resiliency (SIRR), outlined a "layered strategy" that includes Staten Island-specific projects to add sand dunes and to raise and armor the South Beach boardwalk with sturdy structures in preparation for future storms. He said:
Integrating that into the boardwalk would provide protection for a large portion of the East Shore of Staten Island. The Army Corps has actually been looking at that project since the 1990s. That project needs to be moved forward. When the Army Corps is involved, there is a lot of process involved, and sometimes that can delay projects that, even if people think there is a lot of sense behind it, there may be a lot of issues that will stall it.
Not Sufficient? But those improvements won't be sufficient, according to Mike Abrahams, technical director for structures at the engineering firm Parsons Brinckerhoff:
That would improve conditions and it would help improve the vulnerability to smaller storms.But my thesis is that those types of measures, while they are helpful, don't really address the long term problems that we are facing.
Abrahams said not only will the effects of global warming and rising water levels make Sandy-sized storms more frequent, they will also allow smaller storms to inflict similar damage:
The 100-year storm now has to be considered a much more frequent storm. The 10-year storm becomes the three-year storm, and so on.
Abrahams introduced to the audience on the Zephyr his plan to install three floodgates in major city waterways. The gates would be similar to those constructed in London and those proposed for cities like Saint Petersburg, Russia, and Venice, Italy, designed to protect coastal cities from surges and wave action caused by storms Sandy-sized and above.

Located in the East River, the Kill van Kull and either the Arthur Kill or the waters off Sandy Hook, N.J., the gates would protect New York City in ways the mayor's plan could not, Abrahams said. Buts the project's projected price tag of around $20 billion that makes its completion improbable.

Dr. Philip Orton, a research oceanographer at Stevens Institute of Technology in Hoboken, N.J said:
It is definitely not something to forget about. The city decided to forget about it, right?
Abrahams believes there are multiple reasons why this is. For one, there is environmental concern that the massive water gates -- which would need to protrude more than 20 feet out of the water -- would negatively affect water flow and marine life. There is also the ignorance that stems from the uninformed belief that New York cannot suffer from another Sandy, he said.

Hit Again?

"It is really hard for people to grab onto the idea that we can get hit again," he said.

Finally there is the cost. Abrahams says:
In fact $20 billion is not a large amount of money for this. We've already spent that much on Hurricane Sandy. If you look worldwide and see what other major cities are doing, then maybe a different solution will appear more acceptable.
Haas said the gate option will be further investigated, but advocates the mayor's plan for its wide-ranging intentions.

The layered approach really looks at protecting the coastal edges, while also looking at building level protections and infrastructure protections. In lieu of one large, mega-project, a number of interventions and improvements that protect neighborhood-wide, area-wide, can really improve conditions. It's nearly impossible to climate-proof New York City. Somehow, Mother Nature is going to bring something that is beyond what was anticipated.

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