A valuable new study by researchers at Tulane University suggests that Louisiana will not be able to build land fast enough to keep up with how quickly wetlands are disappearing.
Published recently in the journal Science Advances, the study's implications are serious for the latest version of the state’s Coastal Master Plan, a $50 billion blueprint designed to save as much of the coast as possible. But few believe complete restoration is possible.
The authors of the study agree with scientists who say river diversions are the best way to sustain portions of the Mississippi River Delta. But even the best-built diversions won’t deposit sediment quickly enough to save the entire coast, they say.
“The river is capable of building land,” Elizabeth Chamberlain, who led the study, told reporters from The Lens, “but the rates at which it’s building aren’t high enough to offset the rates of loss we’re seeing.”
The Tulane study described in The Lens uses new geological methods to assess how fast land was built along Bayou Lafourche over centuries. That rate is important, particularly as the coastline is threatened by the combination of rising sea levels, wave action and tropical storms, and subsidence of the alluvial soils of the coastal zone.
Land loss in coastal Louisiana has averaged 15 to 20 square miles per year over the past century. The latest research from the U.S. Geological Survey shows that number is now close to 10.8 square miles per year.
The combination of factors affecting the coast requires — as successive versions of the coastal Master Plan recognized — "difficult choices" about where to locate diversions, in the words of Tulane geology professor Torbjörn Törnqvist.
Very true, and one reason that Louisiana must be very careful to avoid a political dispersal of projects, rather than focusing the diversions where they are of the most value.
The diversions are intended to mimic the process of distributing river water and allowing its sediments to build land as the Mississippi River once did. The levees that protected the river from flooding were recognized as early as the 1930s as interrupting the natural processes of land-building.
One of the biggest such projects is in Barataria Bay, to be funded with settlement payments from the 2010 BP oil spill. The Trump administration is working to fast-track the engineering and environmental approvals for the project.
However, diversions may not be possible everywhere — not only for reasons of costs, but as the Tulane study implies, because in some places they might be as ineffective as King Canute's men flogging the water to hold back the tide.
Louisiana faces a multi-generational task in coastal protection and preservation. Wise choices have to be made about where to focus inherently limited resources of money and time on coastal rebuilding projects.