During storms, sand dunes can be a primary defense for coastal communities, but there is limited research on how different types of dunes will respond to extreme weather. With support from the National Science Foundation, Dan Cox, professor of coastal and ocean engineering and principal investigator, and Meagan Wengrove, assistant professor of coastal and ocean engineering and co-PI, are leading a project to learn more about how these natural features can better protect coastal areas.
This year at the O.H. Hinsdale Wave Research Laboratory, Wengrove and a team of 20 students from throughout the U.S. hit three types of dunes — vegetated, bare, and bio-cemented — with hurricane-scale waves on the same order as an El Nino storm. Bio-cementation is a way to strengthen sands using microbial processes. Matt Evans, professor of geotechnical engineering, is co-PI on a coinciding NSF project, using the same dune, to assess the performance of bio-cementation.
“We looked at how the big waves affected the erosion of the dune, specifically to understand if the vegetation or bio-cementation could stabilize the dune better than if there were no plants in place,” Wengrove said.
Researchers from Oregon State, the University of Delaware, and Texas A&M University constructed a greenhouse over top of the testing area and grew plants in place for six months to create the vegetated dune before they ran waves against it.
“We instrumented the dune with buried sensors, measuring moisture content, pressure, and acceleration,” Wengrove said. “Previous studies have only really looked at erosion from the surface. In this case, we looked at it from inside of
In addition to providing coastal protection, sand dunes are an appealing option for coastal managers because they offer a habitat for plants and animals.
“Instead of a seawall, which is more of a gray structure, a sand dune is more of a green structure, so it’s more resilient,” Wengrove said.
“This is one of the first comprehensive studies of the role of natural and nature-based features for coastal protection against hurricane wave and surge,” Cox said. “This new research allows engineers and land-use planners to quantify the benefits of these features in the design of coastal infrastructure to make communities more resilient.”
The experimentation phase of the research concluded this summer and now graduate students and PIs from across the country are processing the data.
“We hope this research will help us to better understand how dunes will erode or could be more robust along the U.S. and other parts of the world,” Wengrove said.
by Johanna Carson
Civil and Construction Engineering News, Winter 2020
Tuesday, Dec. 31, 2019