A new study shows that coastal communities may be more at risk from sea level rise than previously thought. This could have profound effects on US real estate, infrastructure and the economy.
Sea levels are rising as the earth warms and glaciers melt. At the same time, the land is sinking—yet another damaging effect of climate change. According to a new study by Virginia Tech and the US Geological Survey, it is sinking as much as five millimeters a year in some areas. Sea level rise is about three millimeters a year.
“What we found is that most of the land around the United States, and indeed globally, is receding, shrinking. And this downward movement is increasing the rate of relative sea-level rise in many locations around the world, especially along the East Coast of the United States,” said Manoochehr Shirzaei, Associate Professor of Geophysics and Remote Sensing at Virginia Tech.
Shirzaei and his team used space-based radar satellites to build digital maps of the earth over many years to see where it is sinking the most. They then produced the first high-resolution maps of it, showing the east coast sinking anywhere from two millimeters to five millimeters a year – affecting more than 2 million people and 800,000 properties.
The study says that when land subsidence is added to sea-level rise, it doubles the frequency of flooding and halves the time it takes cities and coastal residents to prepare. This has implications for flood adaptation strategies that have already been developed. Areas including New York’s JFK and LaGuardia airports are seeing land subsidence of more than 2 millimeters a year.
“So with sea level rise, for example, at a rate of five millimeters a year, we have X number of years in the future to deal with that, to prepare for this doubling of flood frequency. Now imagine in the same location the earth it is receding at a rate of five millimeters a year,” he said.
In Baltimore, Maryland, so-called nuisance flooding is becoming more common due to rising sea levels and sinking land.
“When you have nuisance flooding, it basically means it’s a nuisance,” said Grace Hansen, coastal planner for the city of Baltimore. “But when you think the boardwalk here is flooded, you know, some people can’t get to businesses or can’t go to work.”
Coastal Baltimore is sinking more than two millimeters a year, according to the study.
“To me and to you, that doesn’t seem like much, by any means, but what becomes a problem is when it’s not even, and you can sink the foundation of the building faster than the other side of the building, and that’s where” It will I see that the foundation is not solid,” Hansen said.
Why is the earth sinking?
Climate change is causing drought, forcing us to pump more groundwater and build more dams to store water.
“Warmer temperatures and lower rainfall increase the demand for fresh water, and the main source of that in most places is groundwater. So we’re pumping groundwater to meet that demand, and that’s accelerating the subsidence or subsidence of the land due to compaction.” of the aquifer,” Shirzaei explained.
In addition, dams are being built to conserve water and generate electricity. During the transition to cleaner energy, the demand for electricity increases dramatically. These dams reduce the sediment supply to coastal areas and starve them of sediment. As a result, the earth sinks even more.
“In terms of groundwater extraction, that’s primarily one of the reasons why Baltimore is sinking,” Hansen said.
More than six dams surround Baltimore.
Even as water becomes scarcer, Shirzaei says land subsidence must be mitigated over the next decade or it will seriously affect the integrity of buildings and infrastructure.
“It would affect bridges, pipelines, railroads, airport runways, and that would translate into trillions of dollars in loss and repair costs,” he said.
Some of Shirzaei’s proposals include recycling water with sewage and sewage treatment, introducing broader restrictions on water use, especially in landscaping, and recording rain and better storing it. A project in Virginia pumps groundwater back into aquifers and treats it at wastewater facilities.
Whatever the choice, he says, the sinking must stop.
CNBC Senior Producer Erica Posse contributed to this piece.