Two new studies led by former Tulane University students shows the benefits of using river diversions to build back Louisiana’s sinking wetlands.
The studies published in the Journal of Geophysical Research: Earth Surface, focuses on subsidence in Louisiana’s coastal wetlands and shallow bays at the Mississippi delta.
The studies used a data method called borehole which collects samples from deep in the ground, then analyzed for numerous characteristics, including sediment density and age.
On study says:
We find that highly organic sediments are particularly susceptible to compaction, especially when they are buried by sand or mud. As a result, deltaic wetlands cannot rely on organic matter alone to keep pace with sea-level rise. These findings are relevant to delta restoration efforts where sediment is reintroduced to previously isolated wetlands to combat wetland loss.
“We found that both wetlands and bays subside rapidly due to loading with fresh sediment,” said co-author Torbjörn Törnqvist, Vokes Geology Professor in Tulane’s Department of Earth and Environmental Sciences. “The wetland study led by Keogh shows that the majority of this subsidence happens in the shallowest 10 feet and within the first centuries after deposition. The shallow bay study led by Chamberlain shows that up to half the elevation gain that is possible by deposition is lost to subsidence.”
“Much has been made of processes deeper in the Earth’s crust like faults, but the available research that attaches hard numbers to deep processes shows that those are secondary factors,” Törnqvist added. “Shallow processes are not only much more rapid, often by a factor of 10, but also occur almost everywhere along our coast and they are demonstrably ongoing today.”
