Highlights
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Land in some coastal areas is sinking faster than scientists once thought.
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A research team that includes UCF Associate Professor Thomas Wahl found that sinking land and rising sea levels are occurring more rapidly, increasing the risk of flooding.
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Understanding these changes can help communities better prepare for flooding and protect infrastructure.
For almost a century, researchers have known that vertical land motion 鈥� the lifting and sinking of the ground 鈥� affects sea level locally. As the ground sinks, the sea level rises relative to the land. Scientists also assumed this process generally occurred at a steady rate over time. But a research team that includes Thomas Wahl, a UCF researcher and associate professor in the , has found that ground subsidence has undergone phases of variable change, creating significant implications for coastal communities.
“In many places, … sea level is going up one to three millimeters a year, but the land is going down 10, 15 times as fast.”
In an article recently published in Nature Geosciences, Wahl and his research collaborators demonstrate that the rate of vertical land motion is nonlinear in many coastal communities, particularly in Louisiana and along the Mississippi Delta. As the land sinks, relative sea level rises, increasing the risk of coastal flooding from high tides and storm surge that can damage homes, businesses and critical infrastructure.
鈥淚n many places like Louisiana, sea level is going up one to three millimeters a year, but the land is going down 10, 15 times as fast,鈥� Wahl says. 鈥淎nd that compounds the effect of sea level rise. As the sea level goes up and land goes down, you have a bigger problem.鈥�
A New Challenge for Coastal Communities
“Our results reveal that … groundwater extraction and … earthquakes have led to periods of rapid sinking or rising of coastal land.”
Current projections of future sea-level change typically assume that ground motion behaves linearly over time. However, the study challenges that assumption. Using observational data from tide gauges, the team, led by Associate Professor S缨nke Dangendorf of Tulane 海角直播, reconstructed vertical land motion dating back to the early 20th century.
鈥淥ur results reveal that human activities such as groundwater extraction and natural phenomena such as earthquakes have led to periods of rapid sinking or rising of coastal land,鈥� Dagendorf says. 鈥淭his has largely increased the rates of sea level rise relative to the land, particularly in cities where increasing water demand led to increased groundwater withdrawals and subsequent compaction of the ground.鈥�
The Silver Lining
Wahl says these findings have important implications for coastal infrastructure, including in Florida.
鈥淚t makes it even more critical to plan early and to create adaptation strategies to keep the water away from places where you don鈥檛 want it to be for as long as you can,鈥� Wahl says.
The silver lining, he says, is that some causes of land motion can be managed. Cities such as Tokyo and Shanghai once experienced extreme subsidence 鈥� up to several centimeters per year during the mid鈥�20th century 鈥� but have dramatically slowed the sinking after implementing strict groundwater extraction controls and related land鈥憁anagement policies.
When it comes to addressing the combined challenges of sea level rise and land subsidence, Wahl acknowledges that some areas will be harder to protect than others, and that protection may not be possible everywhere. Still, he remains hopeful.
鈥淗istory has shown that humans are very creative, especially when they have to be,鈥� Wahl says. 鈥淚f you look back to where we were 100 or even 50 years ago and where we are now, there are probably technologies and strategies that we haven鈥檛 even thought of yet that might come up in the future that will be beneficial in that context.鈥�
About the Researcher
Wahl collaborated on the study with researchers from Tulane 海角直播, Harvard 海角直播 and various academic and research institutions in Germany and the Netherlands. Prior to joining UCF in 2017, Wahl was a Marie Sklodowska Curie fellow of the European Union at the 海角直播 of Southampton and a postdoctoral scholar at the 海角直播 of South Florida. His research focuses on coastal flood risk, sea level rise and storm surges.
