Turner and researchers Joseph J. Baustian, Erick M. Swenson, and Jennifer S. Spicer conducted their study in November 2005, soon after Katrina and Rita struck (Hurricane Katrina and Hurricane Rita complete coverage.)
Katrina made landfall on August 29, 2005, on Louisiana's eastern coast near the mouth of the Mississippi River (Louisiana map). The storm later made a second landfall on the Mississippi coast (Mississippi map). Hurricane Rita came ashore September 24, 2005, near the Louisiana-Texas border.
Both hurricanes pushed large storm surges onto shore. The surges left behind sand, silt, and dissolved clay.
The research team traveled west from Louisiana's eastern border with Mississippi to a few miles into Texas, collecting 198 sediment samples.
The samples revealed that the hurricanes had dumped from 1 to 6 inches (3 to 15 centimeters) of new sediment in the Louisiana wetlandsabout 144 million tons (131 million metric tons) of new sediment in total, study co-author Baustian says.
"We now have a better appreciation for how much sediment can be added by hurricanes," Baustian said.
Engineers have tried to increase sediment deposits by diverting the flow of the Mississippi River through coastal wetlands. But the LSU researchers say the two hurricanes last summer brought in 227 times more sediment than the river diversions bring in a year.
"The diversions we have now introduce a trivial amount of sediment compared to hurricanes," Turner said.
New Approach to Wetlands Loss
The study authors say their findings mandate a new approach to understanding the loss of wetlands and how to reduce that loss.
They say that the loss of plants and other "organics" could be doing more to diminish wetlands than previously realized.
The plants' roots hold the wetlands in place, Turner says. If the plants are lost, the wetlands lose their stability.
CRCL's Ford says that the role hurricanes play in helping wetlands has not been extensively studied.
But he thinks ecologists and environmentalists will raise questions about the LSU study's conclusions, including whether the estimates for the amount of sediment moved by last summer's storms are too high.
"Turner is very well respected," Ford said. "But not everyone agrees with him."
Still, the LSU researchers' work could prompt more studies of how hurricanes may benefit wetlands, Ford says.
Willie Drye is the author of Storm of the Century: The Labor Day Hurricane of 1935, published by National Geographic Books.
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