Unless you’re sinking into quicksand, you might think the ground beneath your feet is solid and immovable. In fact, “subsidence” may be occurring in the area where you live. This is where the ground collapses as the sediment settles. people are pumping too much groundwater. new york city is sinkingThe weight of all the buildings pushing against the ground is also to blame. In extreme cases, such as California’s agriculturally concentrated San Joaquin Valley, elevations are plummeting by units rather than inches. tens of feet.
Last year, scientists report Along the U.S. Atlantic coast, water is falling by several millimeters every year, and in some areas, such as Delaware, it’s several times that amount. So, just as sea levels are rising, land along the East Coast is sinking, greatly exacerbating the dangers to coastal areas.
with follow up study In a paper just published in the journal PNAS Nexus, researchers tally the increasing costs of land subsidence due to subsidence, groundwater extraction, and other factors for these communities and their infrastructure. Using satellite measurements, they found that up to 74,000 square kilometers (29,000 square miles) of the Atlantic coast are exposed to up to 2 millimeters (0.079 inches) of subsidence per year, impacting up to 14 million people and 6 million properties. I found that giving. And more than 3,700 square kilometers of her land along the Atlantic coast is sinking more than 5 millimeters a year. This is an even faster change than sea level rise, which is currently 4 millimeters per year. (In the map below, warmer colors represent greater subsidence, up to 6 millimeters.)
Every millimeter of land subsidence increases the likelihood of storm surges. This is a hurricane-like wall of seawater. Especially good at pushing onshore— creeping further inland and destroying more and more infrastructure. “And it’s not just about ocean levels,” says Leonard Owenhen, the study’s lead author and an environmental security expert at Virginia Tech. “For example, it can also disrupt the topography of the land, so when it rains there are areas that can flood.”
A few millimeters per year of subsidence may not sound like much, but these forces are relentless, and unless coastal communities stop pumping groundwater, the land will continue to sink deeper and deeper. As more people around the world move to coastal cities, further increasing demand for groundwater, social forces are also becoming more unrelenting. “Sometimes some processes are cyclical; for example, in the summer, we pump so much water that the land sinks rapidly over a short period of time,” said Dr. Manuchel Shirzaei says. “As a result, large areas will subside below the threshold, resulting in widespread water inundation.” When it comes to flooding, land elevation loss is a slope factor that has been largely ignored in previous studies. , says Shirzaei.
For example, in Jakarta, Indonesia, the land is Subsidence of nearly 1 foot per year Because the aquifer is collapsing. Therefore, within the next 30 years, 95 percent of North Jakarta could be under water.The city is planning a huge seawall to hold back the sea, but It’s no good if we don’t stop the sinking.
The new study warns that levees and other critical infrastructure along the Atlantic Coast are at similar risk. If the land has settled uniformly, it may be possible to continue raising the embankment height and filling it. But a bigger problem is “disparate subsidence,” where different areas of land sink at different rates. Tom Parsons, a geophysicist at the U.S. Geological Survey who studies subsidence but was not involved in the paper, says, “If there are buildings, runways, etc. that are subsidence uniformly, , it’s probably not that big of a deal.” “But if one end is sinking faster than the other, things start to skew.”
