Waves from moderate storms, rather than violent events such as hurricanes, inflict the most loss on coastal wetlands, according to a study by Boston University and the United States Geological Survey.
The biggest cause of salt marsh erosion is waves driven by moderate storms, not occasional major events such as Hurricane Sandy, researchers from Boston University and the United States Geological Survey now have shown.
“Waves are very powerful because they attack the marsh in its weakest part,” says Nicoletta Leonardi, a Ph.D. candidate at BU’s Department of Earth & Environment and lead author on a paper published today in the journal PNAS. “Generally, the more a salt marsh is exposed to waves, the faster it is eroding.”
The study shows that hurricanes and other violent storms contribute less than 1 percent of salt marsh deterioration in those marshes, according to Sergio Fagherazzi, BU Earth & Environment associate professor and co-author on the paper.
Along the New England coast, for example, the moderate northeast storms that may hit every few months strip away far more from the marshes than the hurricanes that may sweep through a few times a decade. “Salt marshes survive for thousands of years, which means they know how to cope against hurricane waves,” he says.
Improved knowledge about salt marsh erosion brings an important new tool to those responsible for management and restoration of wetlands.
Globally, salt marshes are being lost to waves, changes in land use, higher sea levels, loss of sediment from upstream dams, and other factors. Many initiatives around the world now seek to protect and rebuild salt marshes. Evidence also suggests that, at least in some coastal environments, marshes can adapt to rising sea levels.
In the United States, the U.S. Army Corps of Engineers and many cities want to manage salt marshes as “living shorelines” that act as buffers between coastal communities and the ocean, Fagherazzi says.
source: United States Geological Survey