Adding the Right Amount of Sediment to Salt Marshes Keeps Coastlines Afloat
By Madeleine Meadows-McDonnell, College of Agriculture, Health and Natural Resources
Anna Puchkoff in the field conducting a study on sediment distribution in Connecticut wetlands. (Contributed photo)
Adding just the right amount of sediment to the surface of a
Connecticut salt marsh protects coastlines by promoting rapid plant growth,
scientists from the University of Connecticut report in a new study published
recently in Environmental
Engineering.
Adding sediment on top of salt marshes helps them stay above sea
level as it continues to rise. Anna Puchkoff and Beth Lawrence from
UConn’s College of Agriculture, Health and
Natural Resources conducted a study on how the addition of
sediment could restore salt marshes in Connecticut. For her research, Puchkoff
used sediment that was dredged from the Long Island Sound by the nearby
Guilford Yacht Club.
“My goal was to also reduce project costs and replicate a real-life restoration scenario where in many cases, you have to work with what you’ve got or what the available resources at hand are,” says Puchkoff, who recently earned a master’s degree from the Department of Natural Resources and the Environment at UConn. “This was a core principle in my research, since using dredged material from marinas is common and disposal is costly.”
Instead of transporting the sediment to a dumping site, Puchkoff
teamed up with the yacht club to use their sediment to help restore a salt
marsh on their property and reduce sediment transportation costs.
Puchkoff and Lawrence added different amounts of sediment to the marsh – 5, 10, and 15 centimeters – to find out how much sediment is just right. Too little sediment wouldn’t have a large enough effect to outweigh the cost of restoration, and too much could kill the plants and the marsh.
Ultimately, they
found just the right amount. According to their results, five to seven
centimeters of sediment was the optimal amount to increase plant growth, which
keeps the marsh afloat.
“The goal is to find the intersection of where costs are low,
sediment re-application frequency is low, and recovery is high. Our results
indicated that in two years, this amount had the greatest benefit to meet these
goals. Ten centimeters may be a good alternative for a longer time frame,” adds
Puchkoff. The extra sediment has the added benefits of reducing the presence of
plant toxins such as sulfides, and helps the marsh take up carbon from the
atmosphere, she explains.
This study could help coastlines in the Northeast stay ahead of
rising sea levels using techniques that are already in place in other regions.
“Salt marshes are drowning due to rising sea levels, and the Northeastern
coastlines are experiencing higher rates of sea level rise than the global
average,” explains Lawrence, an assistant professor in the Department of
Natural Resources and the Environment and Puchkoff’s advisor.
The management technique of adding sediment to coastal marshes is
commonly used along the Gulf Coast of the US but has only recently been used in
the Northeast.
“I hope this information helps propel coastal wetland restoration
projects from an idea to execution and will provide land managers with guidance
on how to realistically and effectively implement this approach for the
Connecticut coast,” says Puchkoff.