Environmental Exclusive Research Package

Sea Wall, Coastal Mitigation & the Environmental Price

In the aftermath of Hurricane Sandy the loss of life and property highlighted that the proximity to water, which had once made New York City a global economic powerhouse had become a liability and preventative action would be required. Sandy’s destructive power can largely be attributed to a storm surge of about 9 ft.

By Lowell Clare

Hurricane Sandy revealed the extraordinary vulnerability New York City, a city most people had assumed was inviolable, to sea level rise.  It flooded the New York City subway system, and all road tunnels to Manhattan save for the Lincoln Tunnel.  [1] Swaths of the city lost power, thousands of people in midtown Manhattan were evacuated and several large hospitals were closed. Sandy killed at least 43 New Yorkers, left nearly 2 million people without power, and caused approximately 19 billion USD in damages.[2] All told about 51 square miles, or 17% of New York City’s total landmass was inundated. [3] The affected area included almost 90,000 buildings and over 443,000 people.[4]

In the aftermath of Hurricane Sandy the loss of life and property highlighted that the proximity to water, which had once made New York City a global economic powerhouse had become a liability and preventative action would be required. Sandy’s destructive power can largely be attributed to a storm surge of about 9 ft.[5] It is worth noting that the issue of storm surge is not the same as sea level rise. [6] Storm surge is generally understood as the added height of water (above astronomical tides) due to factors associated with storms like wind as opposed to an increase in regular tidal elevations. It makes sense then that after Sandy, as the city considered protective measures for the future they would be focused on other potential Sandy-like events. The Army Corps of Engineers (ACE) was tasked with developing mitigation measures against future storm surge and assessing their long term efficacy. The ACE developed a series of 5 options[7] Ultimately they honed in on “alternative 2,” a combination of traditional engineering embodied by a 6 mile sea wall (roughly half the length of Manhattan) and specific shore interventions throughout the 5 boroughs[8] 

In February of 2020, the federal government abruptly cut off funding for the research and analysis required to pursue this work.[9] Prior to the federal government halting progress on the project the barrier was already hotly contested by environmental advocates. [10] In the first place, the sea wall would only have mitigated some of the effects of a storm surge, it would have done nothing to address general sea level rise.[11] [12]  Moreover, it would have had a deleterious effect on the Hudson River’s ecological health.[13] 

The storm surge barriers, which would have functioned like gates that could separate the Hudson and New York Harbor from the ocean when closed, would have acted like dams even when open. That would inhibit the migrations of fish and wildlife. The obstruction posed by the barrier, even when open, would have trapped sewage and other forms of water contamination closer to the harbor for longer. The reduced movement of the water, and higher levels of nutrients in the water would create ideal conditions for increased algal blooms. [14] In 2013 the New York State Department of Environmental Conservation prepared, “The Hudson River Estuary Habitat Restoration Plan.” [15] Their mandate was to prepare a regional strategy for stewardship of the Hudson estuary. One of the measures they advocate for is removing existing dams to increase naturally occurring sediment buffers along shallow and intertidal habitats that would allow these sensitive biomes to persist with sea level rise. [16] 

In 2019 American Rivers put the Hudson River as second on its annual list of most endangered rivers- the cause was not development or pollution but rather the environmental risks posed by the monumental storm surge barriers proposed by the ACE. [17] In short, the 6 mile barrier would have helped to mitigate storm surge but done little to address sea level rise or protect local marine health. 

That said, New York City (Manhattan especially) is simply too valuable to the regional, national and global economy to allow the sea to overwhelm the area entirely.[18]  While plans for the barrier have been abandoned other mitigation options are being explored. Currently the mayor’s office has a plan to meet the challenge of sea level rise by adding an extra 500 feet of fill for development into the east river. [19]


[1] Hurricane Sandy Shuts Down Transportation, Nearly Every Bridge, Tunnel and Major Roadway Closed.” Pete Donahue. New York Daily News. October 29, 2012. <https://www.nydailynews.com/new-york/holland-battery-tunnels-close-2-p-m-article-1.1194698&gt;

[2] “A Stronger, More Resilient New York, Sandy and its Impacts.” NYC Special Initiative for Rebuilding and Resiliency. Office of the NYC Mayor. June 11, 2013. https://www1.nyc.gov/site/sirr/report/report.page

[3] “A Stronger, More Resilient New York, Sandy and its impacts.” P 13.

[4] “A Stronger, More Resilient New York, Sandy and its impacts.” P 13.

[5] “Tropical Cyclone Report: Hurricane Sandy (AL182012), October 22-29, 2012. Eric S. Blake, Todd B. Kimberlain, Robert J. Berg, John P. Cangialosi and John L. Beven II. National Hurricane Center. February 12, 2013. . P 8 https://www.nhc.noaa.gov/data/tcr/AL182012_Sandy.pdf

[6] Sea level rise is the general increase of the volume of water in the world’s oceans. 

“Could Massive Storm Surge Barriers End the Hudson River Revival?” Elizabeth Royte. September 24, 2019.  Yale Environment 306. https://e360.yale.edu/features/could-massive-storm-surge-barriers-end-the-hudson-rivers-revival

[7]NY & NJ Harbor & Tributaries Focus Area Feasibility Study (HATS). US Army Core of Engineers , NY District. Last Updated April 2020. https://www.nan.usace.army.mil/Missions/Civil-Works/Projects-in-New-York/New-York-New-Jersey-Harbor-Tributaries-Focus-Area-Feasibility-Study/

[8] Areas Benefiting from Each Proposed Study Feature within Alternative #2- NY/NJ Harbor and Tributaries Study. US Army Core of Engineers, New York District. January 2019. https://www.nan.usace.army.mil/Portals/37/20190308_FINAL_HatsAlt2_AreasBenefitingByFeature.pdf

[9] After Trump Mocks Seawall in New York Project is Shelved. Anne Bernard. The New York Times. Febuary 26, 2020. https://www.nytimes.com/2020/02/25/nyregion/sea-wall-nyc.html

[10] “Storm Surge Barriers Threaten the Very Life of the Hudson River.” River Keeper : NY’s Clean Water Advocate,https://www.riverkeeper.org/wp-content/uploads/2018/09/Final-Storm-Barriers-Fact-Sheet-E.pdf

[11] “New York-New Jersey Harbor and Tributaries Coastal Storm Risk Management Feasibility Study: Interim Report.” US Army Core of Engineers: New York District. February 2019. P 16. https://www.nan.usace.army.mil/Portals/37/docs/civilworks/projects/ny/coast/NYNJHAT/NYNJHAT%20Interim%20Report%20-%20Main%20Report%20Feb%202019.pdf?ver=2019-02-19-165223-023

[12] United States, Congress, Office of the Comptroller , and Scott M Stringer. New York- New Jersey Harbour and Tributaries Coastal Storm Risk Management Feasibility Study Interim Report, 23 Oct. 2019. comptroller.nyc.gov/wp-content/uploads/2019/11/Army-Corps-Letter-10-24-19.pdf.

[13] Could Massive Storm Surge Barriers End the Hudson River Revival?” Elizabeth Royte. September 24, 2019.  Yale Environment 306 https://e360.yale.edu/features/could-massive-storm-surge-barriers-end-the-hudson-rivers-revival

[14] Hudson River Named one of America’s most Endangered Rivers for 2019. April 16, 2019. America’s Rivers. https://www.riverkeeper.org/news-events/news/preserve-river-ecology/hudson-river-named-one-of-americas-most-endangered-rivers-of-2019/

[15] Miller, Daniel E., 2013. Hudson River Estuary Habitat Restoration Plan. New York State Department of Environmental Conservation, Hudson River Estuary Program.

[16] Hudson River Estuary Habitat Restoration Plan(31).

[17] America’s Most Endangered Rivers of 2019 Spotlights Climate Change Threats. Christopher Williams. April 16, 2019. https://www.americanrivers.org/2019/04/americas-most-endangered-rivers-of-2019-spotlights-climate-change-threats/

[18] Lower Manhattan Climate Resilience Study. Mayor’s office of Recovery and Resiliency, NYC Economic Development Corporation and Governor’s Office of Storm Recovery. March 2019. https://edc.nyc/sites/default/files/filemanager/Projects/LMCR/Final_Image/Lower_Manhattan_Climate_Resilience_March_2019.pdf

[19]Climate Change: How Can Manhattan be Protected? Make it Bigger? William Neuman and Jeffry C. Mays. March 14, 2019. https://www.nytimes.com/2019/03/14/nyregion/manhattan-climate-change-hurricane-sandy.html

This research article is one in a series undertaken by Unbuilt Labs in support of the graphic novel Post York written and drawn by James Romberger, with creative insights and music from Crosby, aka ClockWork Cros. The experimental comic is published by Berger Books at Dark Horse Comics


Image from Post York by James Romberger