New York City is Sinking

Hurricane Sandy, later named Superstorm Sandy in honor of its widespread destruction, targeted eight countries and 24 different U.S. states along the East Coast in October of 2012, subjecting millions of people to property damage and severe flooding. When the storm hit New York over the span of two days on October 29, 2012, 300 homes were destroyed, hundreds of thousands of people suffered from food shortages and power outages, and crucial city infrastructure was left in ruins. Economic impacts were also severe. Wall Street was closed for two days, and property damages amounted to about $19 billion. In order to prepare for similar extreme weather events in the future, the NYC Economic Development Corporation and the NYC Mayor’s Office of Recovery & Resiliency published the Lower Manhattan Climate Resilience Study (LMCRS) in March of 2019. The study revealed some of the city’s serious blind spots and vulnerabilities to climate change. 

The LMCRS identified the extent to which climate change threatens the future of Lower Manhattan post-2050 and outlined what city officials can start doing now to adapt to these threats in the long term—planning for the creation of urban spaces, for example, will address climate issues while providing the people of Lower Manhattan with safer environments that double as parks and public recreational facilities. Scientists analyzed patterns from satellite data and predicted that by the year 2100, sea levels could rise as much as a foot. This would put 50 percent of the buildings in Lower Manhattan, collectively worth about $14 billion, at risk of damage from storm surges and flooding. During storm surges, strong winds can blow water onto land and cause flooding. Low air pressure in the eye of the storm makes water levels even more uneven—when strong winds spiral out around the eye, surrounding water is pushed down and the water underneath the eye swells up. This dome can travel with the storm as it makes its way onto land. Scientists have also used mathematical global climate models and satellite data to map out where exactly sea levels will rise and potentially lead to inundation. The results show that 10 percent of properties in Lower Manhattan will face daily flooding, and 40 percent of the streets will be damaged by increases in underground water level. 

New York, which was covered by an ice cap in the last ice age (along with much of the East Coast), is already seeing the effects of subsidence as the boroughs steadily lose elevation. Subsidence is the process in which the Earth’s crust gradually caves in due to changes in land composition. In New York, this is happening as a form of glacial isostatic adjustment, a geological process in which land that has risen after being initially covered by an ice cap reverts to its original shape, sinking back down to prior levels.

Human activity also plays an important role in subsidence. In a recently published 2023 study, researchers Tom Parsons, Pei-Chin Wu, Meng (Matt) Wei, and Steven D’Hont estimated that all the buildings in New York collectively weigh about 1.7 trillion pounds, much of which comes from famous landmarks like the Empire State Building and the World Trade Center. The weight of these structures contributes significantly to the one to two millimeters that New York has been sinking each year. However, towering skyscrapers aren’t the only reason behind the sinking. Many of the city’s buildings also rely on the extraction of groundwater to supply running water. When the ground is depleted of moisture, sediments become more pressurized, contributing to the sinking. Conditions are further exacerbated when coastline soil is made of highly compressible materials and cannot sustain the heavy structures that are built on it. 

To make matters worse, the majority of New York City’s coastline is made of clay, silt, and artificial fill, which are relatively soft materials that provide less resistance to subsidence compared to substances like sand or gravel which are harder to squish together. In Queens, for example, the land under LaGuardia Airport, made of artificial fill layered over clay and silt deposits, has been sinking 3.7 millimeters per year, above New York’s annual average of one to two millimeters. This has raised concerns for many of LaGuardia’s building officials, who launched a nine-year, $8 billion renovation project that was recently completed in July 2022. Engineers constructed a concrete floodwall, installed better drainage systems, and renewed energy supply by replacing generators. Despite these efforts, however, flooding continues to plague the heavy building—in September 2023, LaGuardia Airport’s Terminal A was flooded by heavy rainfall, which left travelers ankle-deep in water, making headlines all over the media. 

While the city sinks, water levels are also rising at the same rate of one to two millimeters each year. Combined, these seemingly small rises become more significant and increase the frequency and severity of flooding. Subsidence facilitates flooding by disrupting the slope of floodplains throughout the city. A floodplain is a region of land located next to a body of water that gets submerged when levels get too high due to storms or other weather events. In order for water to drain in coastal areas, floodplains need to have a uniform slope. Subsidence in localized areas contributes to flooding by creating divots in the floodplain that rainwater can collect in, preventing drainage. To avoid damaging important floodplains in cities, officials from the Federal Emergency Management Agency have put building guidelines in place for architects and other professionals to preserve slopes and prevent future floods from being too severe.

Scientists measure subsidence using Interferometric Synthetic Aperture Radar (InSAR). InSAR involves combining two or more SAR images, taken by the NASA satellite NISAR, of the same location at different times from the same viewing position. The images are used to create an interferogram, which highlights everything that has changed between the two SAR images. A SAR image is created when a sensor, in this case the satellite NISAR, sends energy to bounce off of Earth from space and then records how much of the energy is reflected. This gives scientists an idea of what the surface of the receiving land region looks like, providing details about the structure of the land, different levels of elevation, and moisture. Interferograms interpret the differences in the radar wavelengths that the two SAR images record to show what hasn’t stayed the same, which allows scientists to see changes in the land like uplift and subsidence. 

Continuous Global Positioning System (CGPS) is another useful technology when it comes to tracking subsidence. A CGPS station is set up in a specific location and maps the 3D position of a point, reporting data every 15 seconds. This data is combined to give scientists an approximate daily position. The daily positions are then combined into a daily time series, where scientists can see the way the point is changing relative to the ground and, by association, how much the ground is moving. Being able to track subsidence over time using technologies such as InSAR and CGPS lets scientists make important predictions about which areas are the most susceptible to severe flooding, which can help city officials and residents in those areas take the necessary safety precautions. 

Global warming and climate change are also important causes of the increased flooding. Global warming is when greenhouse gases trap solar radiation and its heat rather than allowing it to escape Earth’s atmosphere, causing temperatures to rise. These gases have been accumulating from industrial processes like the burning of fossil fuels, causing temperatures to increase at historically unprecedented rates. In July, August, and September of 2023, average global temperatures were 1.0°C (1.8°F) higher than they’d been averaging since 1850, when temperatures were first recorded. Climate change, often used synonymously with global warming, actually refers to long-term changes in the general weather patterns of a region—while this does happen naturally, global warming has escalated the severity of the changes and the rates at which they’re occurring. For example, wildfires are becoming more frequent and are starting to affect more and more regions more severely. In June of 2023, New Yorkers saw the skies turn orange as smoke from Canadian wildfires was blown south. Stuyvesant students and staff spent a day back in remote learning so they wouldn’t be subject to the pollution on their commutes, and students found themselves attending Zoom calls in place of their classes for the first time since the pandemic. Exceedingly high temperatures are also causing glacier ice to melt in the poles, which adds water to the ocean and causes sea levels to rise. The ocean also absorbs nearly 90 percent of the heat that greenhouse gases trap in the atmosphere, causing water to expand and the global sea level to rise even further.

As a result of all these problems, the Battery Park City Authority (BPCA) has been working hard to develop solutions for the climate problems of the problem. For example, some of the lamp posts along the Hudson River just behind our school are painted blue with signs hanging on them, indicating how high water levels could rise in the next major weather event. These lamp posts help the park defend itself against global warming and climate change. They demonstrate water levels 18 to 23.5 feet above expected levels, stressing the urgency of the BPCA’s project—water this high would be disastrous for the whole city, submerging much of Lower Manhattan and severely damaging infrastructure and the economy. 

The BPCA is currently working to improve the coastline to combat the study’s predictions. The BPCA’s action plan, developed in partnership with the non-profit organization 100 Resilient Cities, contains a section on building the neighborhood’s defenses against climate change that details various developments that the BPCA has in store for the future. The BPC Ball Fields already have a flood barrier system covering their eastern, northern, and southern boundaries, and the construction of a series of flood barriers (concrete walls meant to stop high levels of water from entering the protected area) is underway for a few other locations that are especially vulnerable. Currently, barriers are being added to the Battery Park City Esplanade between First Place and the east side of West Street/Route 9A, which will branch off into North Moore Street (near the Borough of Manhattan Community College and the Independence Plaza) and the esplanade just north of Stuyvesant. There will also be a Southern barrier built from the Museum of Jewish Heritage to the northern border of the Battery.

As Manhattan continues to sink, the effect this has on the city is becoming more and more noticeable. September 2023 featured some of the heaviest rain and flooding the city has seen in over a century, according to Spectrum News NY1’s chief meteorologist John Davitt. Central Park had more than five inches of rainfall, the sixth greatest amount the park has seen since 1882. At JFK Airport, a record was set for rainfall with over eight inches, the maximum rainfall levels recorded since 1948 in the airport’s construction. It rained on 14 of September’s 30 days, which in total amounted to a little over 14 inches of rainfall. The flooding on September 29th alone accounted for over a third of the total rainfall and is the second major flood in the three years since Hurricane Ida in 2021. At this rate, we can anticipate even more severe flooding in 2024 and the years to come.

Stuyvesant itself sits right next to the Hudson River—earlier in January of this year, the path along the Hudson from Pier 40 (the building with the sign that says “I Want To Thank You”) to Pier 51, a similar building further down the path, was flooded with about two and a half feet of water. Our school is just as vulnerable to flooding as the rest of the buildings in the neighborhood. As students, we can help by spreading awareness about the BPCA’s project and volunteering with the BPCA to help keep our city safe.