Several coastal cities around the United States are “disappearing” into the ground, according to new research, which could further exacerbate complications of sea level rise in the near future.
A considerable amount of land in 32 U.S. coastal cities could be at risk of flooding by 2050 due to subsidence, the gradual caving in or sinking of an area of land, according to a paper published Wednesday in Nature.
The continuous loss of land will affect most coastal cities, Leonard Ohenhen, a Ph.D. candidate at Virginia Tech University specializing in coastal vulnerability and large-scale land subsidence, told ABC News.
Large cities surrounded by water — such as Boston, New Orleans and San Francisco — will be among the regions that could experience flooding in the near future due to land elevation changes combined with sea level rise — about 4 millimeters per year, said Ohenhen, who authored the paper.
Up to 273,000 people and 171,000 properties in coastal regions around the U.S. could be impacted, according to the paper’s findings.
Coastal areas with higher elevation levels and lower rates of subsidence, such as the Pacific Coast, are found to have a lower flood threat overall, the study found.
For example, many parts of the mountainous terrain in San Francisco will not have flooding concerns, but the San Francisco International Airport and other parts of the city on reclaimed land are sinking into the surrounding bay, Manoochehr Shirzaei, director of Virginia Tech’s Earth Observation and Innovation Lab, told ABC News.
IN this Dec. 20, 2023, file photo, the left lane is closed as cars commute on Highway 101 near the San Francisco International Airport (SFO) as heavy rain hits San Francisco.
Anadolu via Getty Images, FILE
Conversely, areas with low elevation levels and higher rates of subsidence, such as New Orleans and other areas along the Gulf Coast, were found to have a higher risk of flooding in the future.
New Orleans, for example, is built on low-lying land within the sediments of the Mississippi River, causing the entire city to subside at a rapid rate, said Shirzaei, who supervised the research.
Several locations surveyed on the Gulf Coast show significant levels of sinking — at rates that are equal to or greater than the current rate of global sea level rise, Ohenhen said.
Biloxi, Mississippi, for example, is sinking at about 5 millimeters per year, Ohenhen said.
The main driver of the subsidence is groundwater extraction and compaction of the sediments, Shirzaei said.
Coastal subsidence is often underrepresented in flooding models, the authors said. The inundation coastal regions will experience due to rising sea levels may actually be worse than previously thought when factoring in how rapidly the land is sinking, according to the study.
However, land subsidence will be the key player in elevating flooding hazards in the next three decades, Shirzaei said.
“What happens on the land really, really affects us,” Ohenhen said. “And so if you have a land sinking on one side and see rising on the other side, you’re going to have areas that would be inundated in the future.”
Nearly 40% of the U.S. population lives near the coast, according to the National Oceanic and Atmospheric Administration.
The sinking is expected to cause structural damage to most existing properties, Ohenhen said, adding the paper does not even address the worst-case scenario for many regions.
“As climate change continues to worsen, we are going to see even more worsened effects in most coastal cities,” he said.
People living in coastal regions are already grasping with significant changes, Ohenhen said. In addition, disadvantaged populations, many of which are already disproportionally struggling with the inequalities of climate change, will especially face challenges due to subsidence and sea level rise, the authors said.
Parts of low-lying Florida, such as Miami, are already dealing with “sunny day flooding” that happens as a result of high tide. Miami showed the greatest share of exposure to flooding, with up to 122,000 people and up to 81,000 properties that could be at risk of flooding by 2050, according to the paper.
Local management policies will need to be put in place to fortify coastal infrastructure, as current hazard mitigation efforts are “inadequate,” the researchers said. Among the solutions include installing sea walls, raising existing properties above the flood level and replenishing groundwater supplies, the experts said.
“Land subsidence can be mitigated fairly rapidly using engineering and nature-based solutions that we already have in our toolbox,” Shirzaei said.
A recent study has shed light on a concerning trend that is impacting coastal cities in the United States – sea level rise is causing these cities to sink. The research, conducted by a team of scientists from various universities and research institutions, has revealed that the combination of rising sea levels and subsidence, or sinking of the land, is leading to a significant decrease in elevation in many coastal areas.
The study, which analyzed data from satellite measurements and tide gauges, found that some cities along the East Coast, such as Miami and Norfolk, are sinking at a rate of up to 3 millimeters per year. This may not sound like much, but over time it can have a profound impact on these cities and their infrastructure.
One of the main factors contributing to this sinking is the extraction of groundwater. As cities pump water from underground aquifers for drinking water and other purposes, the land above these aquifers can sink as the water is removed. In addition, the melting of ice sheets and glaciers due to climate change is causing sea levels to rise, putting further pressure on coastal areas.
The implications of this sinking are significant. As the land sinks, it becomes more prone to flooding during storms and high tides. This can lead to increased damage to buildings and infrastructure, as well as threats to public safety. In addition, the sinking of coastal cities can exacerbate the effects of sea level rise, making these areas even more vulnerable to the impacts of climate change.
In response to these findings, experts are calling for action to address the issue of sinking coastal cities. This may involve implementing measures to reduce groundwater extraction, such as investing in alternative sources of water or implementing stricter regulations on water use. In addition, efforts to mitigate the effects of sea level rise, such as building seawalls or restoring wetlands, may also be necessary to protect these vulnerable areas.
Overall, the research on sinking coastal cities serves as a stark reminder of the urgent need to address the impacts of climate change. As sea levels continue to rise and coastal areas sink, it is essential that we take action to protect our communities and ensure their resilience in the face of a changing climate.
