This is what a fifteen-foot wall of water does to the city

A fifteen-foot wall of water starts like this: a hurricane of larger-than-average size spirals up the Atlantic Coast. As it passes New Jersey, a low-pressure system drives the storm eastward into New York Harbor. Due to the size of the storm, an extensive wind field pushes a surge of water toward shore. The storm’s arrival coincides with high tide, and water levels are already elevated; combined with the surge, water levels are record-breaking. The storm is moving fast. The surge peaks just as it reaches land, and a wall of water fifteen feet high slams into New York City with unforgiving force.

This is what a fifteen-foot wall of water does to the city: the water pushes homes off foundations and collapses walls. Hundreds of buildings are destroyed. In high rises, basements flood, breaking mechanical equipment and leaving residents stranded on upper floors. Nearly two million people lose power, heat, and hot water. Highways, railroads, and subway tunnels flood. So do hospitals, and all of the city’s wastewater treatment plants. As do LaGuardia and JFK airports. There are mass outages to phone service and internet. Electrical fires. The gas supply to the city is disrupted for days, and oil refineries shut down for weeks. The coastline erodes. Over 20,000 trees on streets and in parks are damaged. People drown. The cost of recovery will total billions of dollars.

It has happened here before, but never quite like this.


A fifteen-foot wall of water is an estimate for the storm surge created by the 100-year-storm, or the storm that has a 1% chance of occurring in any given year. Coastal storms are becoming more frequent and more intense, and New York City, based on population, is the US city most vulnerable to coastal flooding and sea level rise, according to Climate Central.

The task of protecting the city from coastal storms has fallen to the US Army Corps of Engineers, America’s go-to unit for flood protection and natural disaster response.  

When Superstorm Sandy made landfall in New York in the fall of 2012, the storm led to the deaths of 44 people, inflicted an estimated $19 billion in damages, and destroyed around 300 homes. In the aftermath, President Obama signed the Disaster Relief Appropriations Act of 2013, which directed the North Atlantic division of the Corps of Engineers to conduct a study on coastal storm risk management in the regions hit hardest by Sandy.

From this initial study, New York Harbor emerged as a focus area. Congress authorized the Corps to continue studying the region and come up with solutions to protect New York City from coastal storms.

In 2016, the Corps began the largest civil works project it had ever undertaken. Six years later, in a report nearly 600 pages long—not counting the 13 separate appendices—the Corps revealed their plan to buttress the region from fifteen feet of water. And nobody liked it.


The Corps has a long history of manipulating America’s waterways in the name of flood control. Created by the Continental Congress in 1776, one of the Corps’ first missions was constructing battlements at Bunker Hill during the American Revolution. The Corps soon expanded into civil works projects as well as military, and throughout the 19th and 20th centuries, played a leading role in the construction of railroads, bridges, dams, hydropower, and levees across the country. A description of the Corps’ mission on their website ends with the line: “Through deeds, not words, we are BUILDING STRONG.”

When the floodwalls and levees surrounding New Orleans failed during Hurricane Katrina, the Corps was blamed. They replaced the infrastructure in 2018 with a $14.5 billion upgrade. Less than a year later, the updates were deemed insufficient to keep up with the pace of sea level rise.

For civil works projects, the Corps generally adheres to the ‘3x3x3 Rule’: completing a feasibility study within three years, at a cost of no more than $3 million, with all three levels of the Corps—the district, division, and headquarters, engaged through the process.

Not long into the New York Harbor study, the division requested a funding bump from $3 to $6 million. Despite a pause in federal funding, the Corps moved swiftly, publishing an interim report three years into the study, and selecting a course of action within four. Even with a project of unprecedented scale, by all appearances, the Corps attempted to stick to their usual timeline.


In 2018, the Corps released a handful of PowerPoint slides presenting six options. These options ranged from massive storm gates across the mouth of New York Harbor, to a mixture of gates in the water and on-shore floodwalls, to infrastructure based solely on shore.

One of the six options was a “no action” alternative, which demonstrated what the future will look like without any intervention to serve as the baseline for assessing the other alternatives. Fifteen-foot storm surge or not, the sea level around the city has risen a foot over the past century and is expected to rise by one inch every seven to eight years in the future, according to the NYC Panel on Climate Change. Around 2050, water is projected to break the waterfront edge in the Financial District, and by 2100, high tides would flood two to three blocks inland every day.

Compared to the “no action” alternative, the other options gain an appeal.

“The primary question,” the Corps wrote in a 2019 report, “is the optimal scale of a solution.”

Around this time, certain environmental groups became aware that the Corps was proposing the construction of massive, removable gates at the mouth of the Hudson River. Among the critics of the plan was Riverkeeper, a clean water advocacy organization, which argued that the gates would restrict the natural flow of the river. They began referring to the features as “hell gates,” and launched a campaign that led American Rivers to include the Hudson on the 2019 list of America’s most endangered rivers.

Riverkeeper was joined by other environmental advocacy groups in urging the Corps to increase public outreach and slow down the study. The Corps hosted a series of public forums, which advocacy groups fought twice to extend. Twenty-three municipal governments in the Hudson Valley passed resolutions asking for more time and for more information on the plan. Riverkeeper filed a 72-page letter, detailing their critiques of a “deeply flawed study process.”

The Corps eventually acknowledged that the ‘3x3x3 Rule’ wasn’t going to work and submitted a waiver to increase funding from $6 million to $19 million and push the study schedule from three to six years. The waiver was approved. The Corps received nearly 4,000 public comments on the plan. Months later, a halt in federal funding put the project on pause for two years.


In 2022, the study resumed, and the time had come for the Corps to make a choice.

From the six proposals, the Corps “tried to find that sweet spot in the middle that gave us the best ability to protect the American people,” Colonel Matthew Luzatto said during a January 2023 presentation.

That choice is known as Alternative 3B. 3B, which falls smack in the middle of the spectrum of options, is a mix of in-water and land-based measures. It ranked in the middle of the other options for cost, construction timeline, and the percentage of New York City at reduced risk of flooding from coastal storms—63%–and based on the Corps’ calculus, is the option with the highest cost to benefit ratio.

The hallmarks of Alternative 3B include massive storm surge gates at the entrance of New York Harbor and a 12-to-20-foot-high concrete floodwall that originates at the Brooklyn Bridge, curves around the Battery, and runs along the West Side waterfront to West 34th Street.

“We were charged by Congress to protect against the Hundred Year Flood. Ball park, approximately, that’s a 15-foot storm surge,” Luzatto said. “While we tried to incorporate natural and nature-based features as much as possible, one of the biggest challenges we run into are there are very few natural and nature-based features that are able to mitigate the impact of a 15-foot storm surge.”

Luzatto and his colleagues stressed that these features were a framework, a starting point, but nonetheless a starting point for a design that needed to come together fast.

“We’re very sensitive to the reality that some of these coastal storm resiliency features are not the most attractive things in the world,” said Luzatto.

The Corps opened a second public comment period in 2023. They promised to take the feedback into account, but the project was now entering its final phase, with a Chief of Engineer’s Report due in June 2024.

“It really is a balance that we’re trying to strike,” Luzatto said at the end of his presentation. “How do we protect the people without diminishing their quality of life?”


Alternative 3B did not land well.

More environmental groups began to voice their concern that the storm surge gates would block the tidal flow of the Hudson River. The National Marine Fisheries Service branch of the National Oceanic and Atmospheric Administration worried that the plan would affect marine ecosystems in New York Harbor. The proposed floodwall would cut off a long stretch of the West Side from the waterfront, and potentially disrupt the Hudson River Greenway, the busiest bike path in the country.

Which led Tom Fox, an urban planner who helped create Hudson River Park, to call the plan “the cheapest, most onerous, most controversial project.”

The opposition grew. The community boards along the Lower West Side sent a letter to the governor and to the mayor asking for a different approach. A coalition of 45 organizations called “Rise To Resilience” outlined their critiques in a statement to the Corps: the plan protects some communities while sacrificing others; the plan overlooks nature-based and non-structural solutions; and there is too much focus on storm surge and not enough focus on sea level rise.

Across the board, responses to Alternative 3B touch on similar grievances: the plan came together too quickly, with too little public input, and these large infrastructure projects will fracture communities.

Alternative 3B did not have many fans. But those governmental and regional planning board that did back it recognized its necessity, and offered support – with reservations. “Undertaking such a large and critical effort across a complicated geography is unprecedented for the US Army Corps of Engineers,” the Regional Plan Association wrote on their website. “Yet this is the only study of its kind and plan of its scale for climate adaptation in our region. With it comes the likely promise of federal funds to implement what is sorely needed, protection from the impacts of climate change.”


Project Manager Bryce Wisemiller is, in the end, optimistic.  

“It’s a quite challenging study and I think the vastness of it can seem somewhat daunting,” Wisemiller said in an interview, explaining that the study area is geographically and topographically complex. Five different tributaries feed into the Hudson River. Coastal storms blow into the harbor from Sandy Hook and Breezy Point, while Nor’easters often break through Long Island Sound. On top of this terrain sits the most densely urbanized area in the nation.

“When you start looking at it in details, hopefully the plan that we have is something that can be advanced,” he said, adding, “with a lot of adjustments and changes.”

Wisemiller and his team have proposed large features, floodwalls and storm gates, that can protect New York City from a fifteen-foot wall of water. They have done what Congress asked them to do, using the best tools that they have in the face of a potentially catastrophic problem.

With a mountain of public comments to consider before the final report, Wisemiller is thinking about submitting recommendations to Congress over time, so that the less controversial components can be implemented quickly.

The larger features will take time. Construction is scheduled to begin in 2030, but in the meantime, there are details to work out and there is public support to earn. There is an awareness that whatever the Corp builds will need to be adaptable, to change over time.

“Mother Nature,” Wisemiller said, “always throws curveballs.”