Sinking Cities: Exploring Prominent Land Subsidence Across the United States

This post includes content partially written by AI

Photo byDrew Angerer/Getty Images

Land subsidence, the sinking of land, is a global phenomenon with various causes and consequences. While Southeast Asia has been widely recognized for experiencing rapid land subsidence due to excessive groundwater extraction, the United States is not exempt from this issue. In fact, certain regions within the country face significant land subsidence rates, surpassing the global rise in sea levels. This poses a heightened risk of flooding, particularly in coastal cities. This article examines prominent hotspots of land subsidence across the United States, shedding light on the causes and implications of this phenomenon.

1. Gulf Coast: Houston - A City Sinking Rapidly: Houston, situated on the western Gulf Coast, stands out as one of the locations experiencing the most rapid land subsidence rates in the United States. With an average subsidence rate of approximately 17 millimeters (0.67 inches) per year between 2014 and 2020, certain areas in Houston have witnessed a significant loss of elevation since 1917. Groundwater extraction, especially in the Houston-Galveston area, is the primary cause of subsidence, amplifying the impact of extreme weather events like Hurricane Harvey in 2017.
2. Gulf Coast: New Orleans - Sinking Below Sea Level: Certain parts of New Orleans are grappling with substantial sinking rates, resulting from both natural processes and human activities. Sinking rates vary across the city, reaching up to 500 millimeters (20 inches) over the past two decades. Groundwater pumping contributes significantly to land subsidence in New Orleans, while fault movements further exacerbate the issue. The sinking of New Orleans, combined with rising sea levels, presents a severe threat to the city's vulnerability to floods.
3. East Coast: New York City - The Effects of Glacial Rebound: As the most populous city in the United States, New York City experiences an average sinking rate of 1 to 2 millimeters (0.03 to 0.08 inches) per year. Researchers attribute this subsidence to glacial rebound, a process triggered by the retreat of ice sheets from the last Ice Age. While the sinking aligns with expectations, certain areas of the city exhibit higher subsidence rates due to the weight of buildings, leading to an accelerated rate of sinking.
4. Mid-Atlantic: Norfolk - Sinking Faster Than Rising Sea Levels: Norfolk, located in the Mid-Atlantic region, faces the highest rate of sea-level rise on the East Coast. Land subsidence plays a significant role, with the Hampton Roads area sinking at a rate twice as fast as the rise in sea levels. In Norfolk and Virginia Beach, subsidence rates surpass 3.5 millimeters (0.14 inches) per year. Variations in sinking rates across different sections highlight the complexity of the issue.
5. West Coast: California's Central Valley - Agricultural Impact: While land subsidence is relatively less pronounced on the West Coast, it remains a concern. In California's Central Valley, excessive groundwater pumping for agricultural purposes has led to significant subsidence. Sections of the San Joaquin Valley have sunk by as much as 8.5 meters (28 feet) since the 1920s. Drought conditions intensify the subsidence issues, with rates as high as 600 millimeters (2 feet) per year recorded in certain areas.

Land subsidence is not confined to Southeast Asia; it affects various regions of the United States as well. Houston, New Orleans, New York City, Norfolk, and California's Central Valley are prominent hotspots grappling with the consequences of land sinking. Understanding the causes and implications of land subsidence is crucial for implementing measures to mitigate its effects.

Source:

1. The Washington Post https://www.washingtonpost.com/
2. "Houston, New Orleans, New York City Among Cities Sinking Faster Than Sea Levels Are Rising" - NASA Jet Propulsion Laboratory (https://www.jpl.nasa.gov/news/news.php?feature=7459)