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Published in The New York Times June 15, 2023

Written by Robert Yaro, Metro Flood Defense Board Member, and Daniel Gutman, Storm Surge Working Group Member

Last September, the U.S. Army Corps of Engineers unveiled its proposal to protect the greater New York and New Jersey metro area from the next catastrophic flood. It is an epic plan that includes dozens of miles of floodwalls, levees and berms along the shoreline and 12 storm surge barriers - arrays of movable gates - across entrances to the waterways throughout the region. The plan is estimated to cost a staggering $52.6 billion. It's by far the most expensive project ever proposed by the Corps.

The trouble is that despite its great ambitions, the Corps' plan demonstrates the shortcomings of relying on massive shoreline structures for flood protection...

Click Below to Download PDF of Article from Sunday, June 18 Print Edition

NYT 6-18-23 op ed
Download PDF • 833KB

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March 10, 2023

This month, MFD submitted its public comment on the Army Corps of Engineers Harbors and Tributary Study (HATS) "Tentatively Selected Plan" Alternative 3B (TSP 3B). Click the link to download a PDF, or read here:

Metro Flood Defense HATS cover letter March 2023
Download PDF • 387KB

Col. Matthew W. Luzzatto


US Army Corps of Engineers, New York Division

26 Federal Plaza, Rm 17-302. New York, NY 10278.

Attention: NYNJHAT Study Team, Planning Division

U.S. Army Corps of Engineers 26 Federal Plaza, 17th Floor

New York, NY 10279-0090

Submitted via email to:

Dear Colonel Luzzatto, Mr. Wisemiller and Ms. Alkemeyer:

Metro Flood Defense (MFD) would like to thank the US Army Corps of Engineers New York

District for its efforts to study and design a system to mitigate the impacts of storm surges

and sea level rise on the New York-New Jersey Metropolitan region. The region is the

nation’s most densely populated with almost 20 million residents, the largest economic urban area with a current GDP of $2.5 trillion, and one of the busiest and most complex urban estuaries. As such, it is imperative that a bold and comprehensive plan is pursued in order to protect these various interests. We realize both the complexity and competing priorities you face in this process, and appreciate the difficulties of balancing the long-term protection of New York Harbor and tributaries. We additionally thank you and your colleagues for the opportunity to submit public comments on the Tentatively Selected Plan (TSP 3B) for the NY & NJ Harbor & Tributaries Focus Area Feasibility Study (HATS). Metro Flood Defense is a 501(c)3 non-profit organization with the mission to increase public understanding of the flooding challenges the NY-NJ Metropolitan Region faces in the era of climate change and steadily increasing sea level. MFD advocates for the advancement of science-based strategies designed to protect the entire region from these destructive threats. We translate and transform essential scientific, technological and urban planning issues in a coherent and readily accessible manner. This essential information is made available to elected officials at all levels of government, governmental agencies and workers, commercial, industrial, transportation and insurance sectors, public health and social justice workers, and the wider public of all ages and backgrounds.

The attached preliminary proposal, Regional Layered Flood Defense Strategy, is

co-authored by members of two affiliated organizations: the NY-NJ Storm Surge Working

Group and Metro Flood Defense, Inc. Our coalition consists of leading oceanographic,

weather, climate and ecology scientists, professional engineers (PE), urban planners,

architects, advocates, and social scientists with many years of experience in the estuarine

and urban regional area. This submission is informed by the members’ own areas of

professional expertise.

As representatives of the communities of New York City, New Jersey, and the metropolitan

regional area who will all be impacted by USACE’s proposed intervention, we hope that

the feedback in this letter and attached proposal will play a critical role in the reevaluation

and revision of the USACE’s Tentatively Selected Plan (TSP 3B). Additionally, we look

forward to working with and supporting the USACE during the process as it continues

forward. With our colleagues at the NY-NJ Storm Surge Working Group, we will go into

greater detail on concerns around the USACE’s TSP 3B, the process, and the lack of

adequate community education and engagement.

Our firm and clear position is that this TSP Alternative 3B is fatally flawed. This plan creates

an incomplete and piecemeal approach, leaving many of the region’s major infrastructure

systems exposed, such as subway entrances, LaGuardia Airport, the Hunts Point regional

food markets, Bayonne shipping terminals, as well as waterfront parks and national

landmarks, including the Statue of Liberty, Ellis Island, the Hudson River and Brooklyn

Bridge Parks. They all lie in serious danger of repeated inundations and destruction. TSP

3B additionally leaves dozens of communities and hundreds of thousands of residents -

many of them in low income and minority communities - unprotected from future flooding

from storm surges and sea level rise and intense rainfall events. This is a new form of

“climate redlining” - discriminating against these communities, and is a serious

environmental justice concern. Alternative 3B only protects 63% of the region, a

completely unacceptable level of protection. We stand with the social justice and environmental conservation advocates who demand comprehensive protection for ALL

communities in the region, not just some.

TSP Alternative 3B would also place multiple portions of the region behind seawalls up to

20 feet high, cutting off shoreline communities from their waterfronts. This will inevitably

lead to years or even decades of controversy and delay. Further, many of the Corps’

proposed onshore barriers consist of a multitude of movable walls and other devices that

would need to be activated or deployed hours to days before the arrival of a major storm.

Under this plan, a network of local agencies would be responsible for maintaining and

activating these components. This is highly problematic from not only a practical and

economic standpoint, but also because if only a handful of these devices failed to be

deployed due to suffering from poor maintenance, agency activation delays or

disagreement, or absent employees at critical times, large areas of the City and region

would experience catastrophic flooding. In addition, during extreme rainfall events, similar

to 2021’s Hurricane Ida’s rainfall, the Corps’ tall onshore barriers would impound vast

volumes of storm water as well as backed-up untreated sewage in the communities they

are meant to protect.

Metro Flood Defense supports the ambitious alternative solution which has been proposed

by the NY - NJ Storm Surge Working Group, which would create a system of “layered

defense” to protect the region for the next century and beyond from extreme storm surges,

rainfall events, and sea level rise. This proposal is based in part on the experience of

dozens of flood barrier systems currently installed and successfully operating in both US

and overseas cities.

This proposal has been prepared with input from leading Dutch coastal engineers who

hold the world’s longest uninterrupted track record of protecting major population centers

from both storm surges and sea level rise. This layered defense proposal is described in

the attached report.

This proposed Regional Layered Flood Defense System has four components:

First line of defense: A network of detention basins, swales, green roofs, rain gardens

and other stormwater best management practices.

These will provide additional interior drainage management during coastal surge events

and reduce urban street and basement flooding. Detention basins, green roofs, swales

and other measures will help to reduce interior flooding during intense precipitation events,

such as was experienced during 2021’s Hurricane Ida.

Second line of defense: Nature based systems

Nature-based defenses, including restored or created wetlands, enhanced oyster beds,

and other natural ecosystems can help dissipate wave scouring and beach erosion while

also improving water quality and maintaining a healthy marine ecosystem. Several environmental groups have suggested that nature-based ecosystem services alone will protect the region from flooding. The reality is that such restored wetlands and other so-called natural systems will not reduce storm surges by more than a few inches at best. Deriving benefits from ecological services is desirable, however, they will never protect the region or its citizens from major storm tides of many feet.

Third line of defense: A network of low (3-6 feet high) onshore levees or fortified dunes

These will be constructed in sections of waterfront at low elevation to protect against king

tides flooding experienced along with gradually rising sea levels. These low barriers should

obviate the need for frequent closure of offshore sea gates even as sea level rises decade

by decade throughout the working life of the major sea gate systems. Importantly, from a

community perspective, the low perimeter levees will not obstruct visual access to

waterfronts from coastal communities, in contrast with the high onshore barriers proposed

in Alternative 3B.

Fourth line of defense: Offshore movable sea gates

The fundamental lesson from planners of similar systems in The Netherlands, London UK,

St Petersburg Russia and the US eastern seaboard communities of Stamford CT,

Providence RI and New Bedford MA is that it is necessary to “shorten the coastline” to

make protecting the almost 1,000 mile perimeter of New York Harbor and the lower

Hudson River possible. This is essential to its effectiveness in keeping surges from entering

the Harbor at all. The unique topography and shape of the metropolitan area creates the opportunity to protect many hundreds of miles of shoreline with two sets of movable sea gates (each a combination of navigational sector gates plus a suitable number of adjacent low form-drag horizontal-axis sluice gates to allow healthy tidal flows and river discharges in settled weather) built at the Harbor’s two choke points:

i) The Atlantic Ocean primary line of defense will hold back storm surges originating

in the New York Bight and flowing into the harbor beneath the Verrazano Bridge. It

would be located in the Lower Bay as far away as possible from regions of dense

development (Corps’ Alternative 2), stretching from Breezy Point (on the Rockaway

Peninsula) NY to Sandy Hook NJ (or possibly a shorter barrier, built from Coney

Island to Swinburne and Staten Islands - but with lesser effectiveness).

ii) The Long Island Sound primary line of defense would be located near Throgs Neck

(Corps’ Alternative 2). This one-mile wide sea gate system would protect the region

against devastating storm surges propagating through the Sound and traveling

through the upper East River into the Harbor, to meet the ocean surge in the lower

East River (where the highest Sandy surges were experienced).

Additional benefits of offshore sea gates when built as part of this layered defense system:

First, in settled weather, offshore sea gates would slightly reduce the speed of tidal

streams flowing throughout the Hudson River Estuary. Some environmental groups have

argued that offshore sea gates would seriously restrict tidal and sediment flows, harm

fisheries and hinder the natural flushing of the Hudson River estuary. The reality is that

carefully designed gate piers with low form-drag and skillfully-operated offshore sea gates

would reduce flows by only 10-15% from current levels. Ironically this is approximately the

same as the increase in tidal flows resulting from historic dredging of the deep Ambrose

shipping channel and other channel-dredging projects since the late 19th century.

During extreme weather events, the Lower Bay sea gates will prevent dangerous storm

surges from propagating up the length of the Hudson River, temporarily driving salty water

well into the river’s central reaches, potentially compromising extraction of potable water

and disrupting fin and shellfish fisheries.

Rather than damaging the estuary’s ecological health, the proposed layered defense

system could actually help to restore and protect these systems. In London UK, the

Thames River has seen improved water quality and signs of improving marine life upstream

of its highly effective storm surge barrier in recent years.

Critics of offshore sea gates have also argued that they would retain and lead to backups

in the city’s sewers during major storms. The reality is just the opposite: the two regional

sea gates systems would be open the vast majority of the time during settled weather and

would only be closed at dead low tide a few hours before the arrival of approaching storm

surges. The gates would be reopened a few hours after the winds and surges had

dissipated, releasing the temporarily accumulated waters into the New York Bight as soon

as possible.

When closed, the Outer Harbor and Throggs Neck sea gates would provide what might be

called a huge internal storage basin, holding upstate precipitation discharge flowing down

the Hudson River into the Harbor, while still maintaining impounded waters at near low tide

levels. Treated sewage would be discharged continuously from all discharge points (including combined sewer discharges in held-low receiving waters, avoiding the horrors of

sewer backups).

By comparison, the Army Corps’ Alternative 3B which proposes to build many smaller

barriers across Jamaica Bay, the Arthur Kill, Kill Van Kull, Newtown Creek, Gowanus Canal

and other smaller inlets would inevitably back up treated sewage and storm water in large

areas of the City, coastal New Jersey and many suburbs up the Hudson River.

Flaws in the Corps’ Benefits versus Costs Analyses

The Corps was constrained by restrictive federal regulations that we and the NY-NJ Storm

Surge Working Group allege resulted in a poorly-conceived economic cost/benefit model

that might be appropriate for say a low-density beach community, but totally inadequate

for the nation’s largest metropolitan region.

We believe that the Corps also i) unnecessarily doubled the cost of regional offshore sea

gate systems by adding unjustified induced flooding and residual risk features; and ii) the

projected 25–32 year construction period for regional offshore systems (Alternatives 2 and

3A) severely cut the benefits of these alternatives.

An accelerated construction plan, such as was authorized for the protection of

post-Katrina New Orleans, would reflect more accurately true costs and benefits of a

regional barrier system.

The Corps’ designed and built New Orleans’ $14 billion flood prevention system in less

than five years, when Congress mandated that they did so! An independent analysis by

consulting engineers for the Port Authority estimated that the outer harbor seagate could

be constructed in eight years for a fraction of the USACE’s cost estimate. We believe with

strong Congressional support, a layered - defense regional protection system as we

described above could be constructed in a fraction of the time assumed in the current plan

we allege is flawed.

Houston’s recent flooding experiences, proves that the Corps is capable of meeting the

challenge: Congress has just authorized Houston’s $34 billion “Ike Dike” - the most

expensive project ever recommended by the USACE in its history. Plans for this project

emerged only after the Corps’ initial flood prevention plan died, principally due to extensive

community opposition. However, the Corps’ Gulf Coast colleagues of the NY Division did

get it right on their second try.

Similarly we can save the Metro region with a robust regional plan that, while expensive,

complicated and controversial, will provide by far the maximum protection for generations

to come.

We respectfully request that the USACE reevaluate and redevelop an improved

comprehensive plan to protect the entire Metropolitan Regional New York - New Jersey

area from the extreme flooding the area will inevitably face, for at least the next 100 years.

We believe that the attached proposal outlines such a plan, and we encourage the USACE

New York District to work with us to develop it further and to communicate it to the public.

We look forward to working with you on this next phase of planning for flood defenses.


Sam Jackson

Co-President, Metro Flood Defense



Sally Bowman

Co-President, Metro Flood Defense


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March 7, 2023

Metro Flood Defense has partnered with the NY NJ Storm Surge Working Group (SSWG) to develop a comprehensive plan to protect the NYC Metro Region from sea level rise, storm surge and intense rainfall. In March 2023, MFD submitted this draft to the Army Corps of Engineers for consideration along with a public comment in opposition to the Corps' "Tentatively Selected Plan" of Alternative 3B (TSP 3B).

Click below to download the March 2023 draft report.

[DRAFT] SSWG and MFD Regional Layered Flood Defense Preliminary Proposal March 2023
Download PDF • 39.88MB

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