Millions of people living in US coastal cities could see their homes sink into the ocean in the coming decades, a study warns.
Researchers at the US Geological Survey (USGS) forecast that by 2100, the East Coast will be devastated by rising sea levels, flooding and sinking land.
They estimate that if the sea level rises 3.2 feet by 2100, as the United Nations has predicted, more than 14 million Americans would be affected in places like Norfolk, Virginia to Miami, Florida and New York City.
They estimated that it would cost over $1 trillion of property damage and cause the region to lose up to 80 percent of it’s beaches.
Meanwhile, a separate study found that California’s immense water demands are causing parts of the state to sink at record-breaking rates.
Researchers at Stanford University found that the San Joaquin Valley is sinking at a rate of nearly one inch per year.
The phenomenon, called subsidence, is often caused by removing water, natural gas or mineral resources from the ground.
When water is continuously extracted from the Earth’s surface and isn’t replenished, it causes the sediments to compress, damaging aqueducts and permanently altering aquifers.
‘There are two astonishing things about the subsidence in the valley,’ said the study’s co-author Rosemary Knight.
‘First, is the magnitude of what occurred prior to 1970. And second, is that it is happening again today.’
USGS reported that 70 percent of the East Coast population will be exposed to shallow or emerging groundwater caused by rising sea levels by the end of the century, while coastal storms and hurricanes will increase flooding.
The rising sea levels are primarily caused by global warming that causes the ocean to heat up and melt glaciers while the Gulf Stream current pushes more water toward the shoreline.
Since 1920, sea levels have risen by between six and eight inches, but because of global warming and federal government agencies including the Department of Homeland Security and USGS predicts they’ll rise by another 3.2 feet between 2020 and 2100.
The rising sea levels will vary depending on the coast, with the East Coast seeing 10 to 14 inches between 2020 and 2050 while the West Coast will see an increase of four to eight inches in that timeframe.
The government report also said that major flooding is expected to occur five times as often as it did in 2020 within the next 30 years.
There are roughly 80 million people living on the southeast coast and experts found half will be impacted by flooding alone, according to the study published in Nature Climate Change.
The team warned the rising water levels will lead to major infrastructure damage including roads, buildings and septic systems..
The study’s co-author, Manoochehr Shirzaei from Virginia Tech’s Department of Geosciences said: ‘We need to rethink how we plan and build for the future, especially in highly vulnerable coastal regions.
‘By including a wider range of climate hazards in resilience strategies, we can better protect our communities from the compounded effects of sea level rise and extreme weather.’
However, the researchers did not state what strategies should be implemented to prevent the East Coast from further sinking.
The USGS also reported that subsidence is causing much of the southeast Atlantic coast’s land to sink, which will only worsen the rising sea levels.
Cities most exposed to notable sinking land include Miami, Savannah, Charleston, Myrtle Beach, Virginia Beach and Norfolk.
According to the study, 1.3 million people currently live in these areas where subsidence is exceeding two millimeters per year.
Likewise, researchers found that this has already begun to occur at drastic levels across the San Joaquin Valley in California, damaging local wells and irrigation systems.
San Joaquin Valley’s arid climate and a series of droughts has made it necessary to pump out groundwater to support major agricultural land across the US, which have caused permanent changes to the valley’s topography.
Stanford researchers estimated that about 220 billion gallons of water are needed annually to prevent further subsidence.
When water is extracted from natural reservoirs called aquifers it causes the land to lose it’s shape and sink.
This is because aquifers contain sediments which have pores, much like a sponge, and when the water isn’t replenished, those spaces will compress and permanently alter it’s ability to carry water.
This is seven billion gallons less than the amount of surface water that’s left over in the San Joaquin Valley after all other environmental needs have been met each year.
However, Knight said she is hopeful that steps can be taken to prevent the land from continuing to sink.
‘My group and others have been studying this problem for some time, and this study is a key piece in figuring out how to sustainably address it,’ she said.
The researchers tracked elevation changes in San Joaquin Valley using satellite technology called interferometric synthetic aperture radar (InSAR).
The system noted the changes by transmitting radar signals from Earth’s orbit and analyzing the reflections to measure how much the ground had shifted from 2006 through 2022.
Over the last two decades, researchers have known that the valley was sinking, but this is the first time they used satellite radar systems to confirm it.
Although there was a gap in data from 2011 through 2015, the team was able to estimate how much the land sank before and after that timeframe.
From 2006 through 2010, they reported that the San Joaquin Valley sank by 4.2 cubic feet and sank another 2.8 cubic feet between 2015 and 2022.
‘How much was last year’s flooding worsened by? How much are farmers spending to re-level their land? A lot of the costs of subsidence aren’t well known,’ highlights Matthew Lees, the study’s lead author.
Their findings mirror a similar event that occurred between 1925 and 1970, when groundwater pumping caused more than 4,000 square miles to dramatically sink by up to 30 feet.
According to the study published in the journal Communications Earth and Environment, the researchers recommend implementing a flood-managed aquifer recharge (flood-MAR).
This would strategically divert excess water from rain and snowfall to replenish the groundwater in areas that are sinking.
‘We should be targeting the places where subsidence will cause the greatest social and economic costs,’ Knight explained.
‘So, we look at places where subsidence is going to damage an aqueduct or domestic wells in small communities, for instance.
‘By taking this Valley-scale perspective,’ added Knight, ‘we can start to get our head around viable solutions.’
