NYC Flood Risk and Sea-Level Rise

Flooding is when water goes where it shouldn't, like onto normally dry land. It can happen because of heavy rain, waves from the ocean, fast-melting snow, or broken dams. Floods can be really damaging, covering homes or land with water, and they can last for different amounts of time. The most dangerous kind is a flash flood, which happens super quickly when there's too much rain for the ground to soak up or when rivers overflow fast. Flash floods are very fast and can be very dangerous (NOAA, 2023).

1. River flood - happens when water exceeds the river bank's height, often due to heavy rain, storms, snowmelt, or ice jams.

2. Coastal floods - result from elevated high tides, amplified by heavy rainfall and onshore winds. Frequent in areas like Charleston and Savannah due to coastal development and low elevation.

3. Storm surge - an abnormal coastal water level rise driven by severe storm winds, waves, and low pressure. It poses a significant threat, potentially causing extensive flooding and damage during events like hurricanes, such as Hurricane Katrina in 2005.

4. Inland flooding - happens when prolonged or heavy rainfall, river overflow due to various factors, or dam failures lead to significant water accumulation, often causing extensive damage as seen in events like Hurricane Floyd in 1999.

5. Flash flood - results from rapid, heavy rainfall within a short timeframe, often causing sudden and violent torrents of water through various terrain, including urban areas or canyons. It can occur rapidly, sometimes even without rain, due to factors like dam failure or debris jams.

New York City is divided into five boroughs or counties. Below, is a detailed map showcasing the specific areas and neighborhoods within each of these five boroughs, allowing you to explore.

Over the years, several types of floods have occurred in New York City. Here are the worst flash floods that have hit the city.

• NYC Flash Flood (July 2022)

In July 2022, heavy rainfall led to flash floods in NYC, causing subway stations to flood and a significant sinkhole to emerge in the Bronx, but fortunately, there were no injuries reported.

• Hurricane Idalia(September 2021)

Hurricane Ida had devastating effects, causing widespread destruction in Louisiana, with over a million people losing power and significant flooding. Its remnants led to severe and unexpected rainfall in New York City, resulting in the city's first-ever Flash Flood Emergency Warning and over 40 fatalities. The Northeast region experienced extensive damage, costing up to $24 billion, including numerous boat rescues, stranded commuters, and significant disruptions in transportation.

• Hurricane Sandy (October 2012)

Hurricane Sandy, which struck New York City in October 2012, resulted in devastating flash floods and long-lasting consequences. The storm surge reached 13 feet and was exacerbated by a full moon and higher tide, causing widespread flooding. Lower Manhattan and Staten Island were the hardest hit, with over 40 casualties in the city. The South Ferry/Whitehall subway station, renovated after 9/11, was submerged and remained closed until 2017.

Sea level rise in New York City results from a combination of factors, notably the slowing of the Gulf Stream and land subsidence. Winter storms, known as nor'easters, intensify flooding by raising high tides due to the moon's gravitational pull. With a 9-inch sea level increase since 1950.

Addressing this issue is complex due to the city's unique infrastructure and its impact on nearby areas. Over the past decade, sea levels have risen by about 1 inch every 7-8 years, and a further 6-inch rise is expected within 14 years. However, the exact rate of ocean warming and ice melt remains uncertain, leading to a range of predictions, with the US Army Corps of Engineers' high forecast considered the most likely scenario. Below is an interactive map representing sea level rise prediction for the year 2080.

New York City (NYC) is susceptible to increasing coastal hazards, primarily due to sea-level rise and climate change [1] [2]. This project comprehensively analyzes the impact of sea-level rise on flood hazard areas in NYC by utilizing available GIS data. Sea-level rise poses a significant threat to NYC’s coastal areas, leading to an increased risk of flooding [3]. Understanding the potential flood hazard areas under different sea-level rise scenarios is crucial for effective urban planning, risk mitigation, and disaster preparedness [4]. The Analysis shows about 34.8% of the land area in New York City is at risk.

This analysis is calculated using the below map which represents the loss of land that can occur if the sea levels rise according to the prediction.

As stated earlier, the Sea level is rising every year. Global mean sea level has risen about 8–9 inches (21–24 centimeters) since 1880. Here is a map representing the standard deviation from the current sea levels and the predicted sea level rise. This map showcases the severity level of flood risk in certain areas of New York City.

In summary, our in-depth study of flood risk and sea-level rise in New York City highlights a concerning truth. The projections for the city's sea levels show a significant increase in vulnerable areas. This problem isn't limited to New York City; it affects many other cities globally, all facing the looming threat of submersion and flooding due to rising sea levels. A focused examination of New York City serves as a microcosm of a global crisis that urgently requires attention and decisive action.

Top 5 U.S. metro cities with most chronic physical risk from climate change hazards