How rising sea levels will affect New York City, America’s most populous city

(NEW YORK) — New York City is among the most densely populated coastal communities in the world preparing for an inevitable rise in sea levels, which scientists said will amplify flooding crises from events such as thunderstorms, high tides and hurricanes.

Sea levels in New York City are expected to rise between 8 inches and 30 inches by the 2050s and as much as 15 inches to 75 inches by the end of the century, according to The NYC Panel on Climate Change.

About 1.3 million residents of New York City live within or directly adjacent to the floodplain, according to Rebuild by Design, a climate research and development group. As sea levels continue to rise, that number could increase to 2.2 million New Yorkers.

The consequences of sea level rise were displayed in 2012, when Superstorm Sandy, a Category 3 storm at its peak intensity, hit New York City as a tropical storm. The system, coupled with high tide, sent a storm surge from the East River into lower Manhattan — more than 9 feet above normal tide levels in Battery Park, while the depth of floodwaters measured at 14 feet in Staten Island, according to a report by the city.

Forty-four residents of New York City died as a result of the storm, officials said.

Since Sandy, the city has moved to flood-proof critical infrastructures, such as hospitals, power plants and major tunnels, which were impassable for both drivers and subways after the storm.

The Army Corps of Engineers has proposed the construction of giant sea gates across New York Harbor. The $52 billion proposal would involve building 12 movable sea gates across the mouths of major bays and inlets along the harbor.

Even with those massive flood barriers, smaller floods will still be able to seep in, Malgosia Madajewicz, an associate research scientist for Columbia University’s Center for Climate Systems Research, told ABC News.

“There is no single factor [that] can eliminate all of the flood risks,” she said, adding that other interventions will need to be utilized, such as smaller infrastructure along the shore and homeowners investing in retrofitting their homes and filling in their basements.

These types of preventative measures could save homeowners hundreds of thousands of dollars over the next decades, said Madajewicz, who researched the cost of damage to homes from Sandy.

However, many New Yorkers struggle to afford the investment necessary to flood-proof their homes, Madajewicz said.

More than half of the New York City residents in the floodplain zone live in areas with a median income of less than $75,120, which is considered low income for New York City for a family of three, according to Rebuild by Design.

In addition, many homeowners may rely on the economic benefits from their basements, which may not be feasible to eliminate from their budget, Madajewicz said.

Those basements turned into death traps in 2021, when the remnants of Hurricane Ida caused devastating flooding in New York City and killed at least 13 people.

While much of the attention around coastal flooding has been around investment in physical infrastructure, social infrastructure is just as important to prepare for the next big storm, Alana Tornello, director of resilience for the Human Services Council and former emergency preparedness lead for the New York City Department of Health and Mental Hygiene, told ABC News.

“There needs to be significant reform and how we get out resources to community partners and to human services organizations,” which includes more voices being brought into adaption planning, Tornello said.

The rate of sea level rise has doubled since 1993, when researchers began taking measurements from satellite images, according to NASA. Anthropogenic, or human-caused, climate change has caused about 270 billion tons of ice mass loss in Greenland per year and about 150 billion tons of ice mass loss in Antarctica per year, according to NASA.

Eight of the top 10 largest cities in the world — Tokyo, Mumbai, New York City, Shanghai, Lagos, Los Angeles, Calcutta and Buenos Aires — are adjacent to the coast, according to the U.N. Nearly 40% of Americans — about 94.7 million people — live in coastal areas, despite those regions accounting for less than 10% of the total land in the contiguous U.S., according to NOAA and the U.S. Census Bureau.

Sea level rise is not just a threat in itself — it is a “threat-multiplier,” United Nations Secretary-General Antonio Guterres said during the Security Council meeting on sea level rise in February.

Rising seas threaten lives and jeopardize access to water, food and healthcare, Guterres said. He said it could also damage or destroy vital infrastructure, such as transportation systems, hospitals and schools, especially when combined with extreme weather events linked to rising global temperatures.

High-tide flooding, or “sunny day flooding,” is becoming increasingly common due to decades of sea level rise, the National Oceanic and Atmospheric Administration said in its 2022 sea level rise report. Rising sea levels are making storm surge brought on by hurricanes more destructive. And 1-in-100-year floods are now happening so often, the term may change, experts told ABC News in 2021.

As a result, coastlines are changing all over the U.S.