Wind tunnel tests Jersey Shore sand, grasses for dune strength

WARETOWN — Inside an old vo-tech garage tucked deep in the New Jersey Pinelands is a Willy Wonka-esque contraption of plywood, plexiglass, and a few high-tech components that may help engineers understand just how coastal dunes – and the dune grass upon them – are built up over time so they can withstand the erosion of the howling winds and waves that rattle the Jersey Shore during ferocious storms.

Here in a building once used for boat storage at the Ocean County Vocational Technical School on Wells Mill Road is the brainchild of researcher Bianca Charbonneau: a 31-foot-long wind tunnel built to test how coastal plants such as American beachgrass and other species build coastal dunes over time.

The hurricane, which struck in October 2012, destroyed much of the state's dune system from Sandy Hook down to Cape May. Along the entire Eastern seaboard, Sandy was responsible for as many as 147 deaths, the destruction of 650,000 homes, and overall damage of more than $50 billion.

"The data we collect from this research ultimately may tell us what we need to know about how coastal plant shape feeds back on and affects coastal dune shape," said Charbonneau. She built the wind tunnel based on a similar one that had once existed at the O.H. Hinsdale Wave Research Laboratory at Oregon State University.

"We need to know everything we can about how dunes are built up and stabilized naturally by plants to make them more effective," she said.

Charbonneau, 27, of Philadelphia, obtained a $42,000 grant from the Army Corps of Engineers in conjunction with the American Shore & Beach Preservation Association (ASBPA) for the project. She is a biology doctoral candidate at the University of Pennsylvania after earning a bachelor's degree in ecology and evolutionary biology from Princeton University in 2012 and a master's degree in biology from Villanova University in 2014.

Nicole Elko, vice president of the ASBPA, said Charbonneau's project and five others were chosen for the funding from a field of thousands of candidates because of the wind tunnel's ability to help researchers "solve real-world problems" with creating sand dunes.

"Ultimately, this project can help to show us how we can build better dunes to create our best line of defense against storms and other disasters along our coasts," Elko said.

Island Beach State Park donated 20 tons of sand and Charbonneau and her team grew about 500 plants of three species — two dune grass varieties and an invasive sedge plant — to test how plant shape feeds back on dune shape.

The tunnel was constructed about a year ago by a crew from Handyman Pros New Jersey, a Parsippany-based contractor, with Charbonneau's oversight and attention to detail for adaptability beyond use for just her research. Wind is generated by a large fan at one end of the tunnel that draws air through a honeycomb-like wall of uniform PVC pipes toward the fan, through the tunnel's chamber, and then outside. The intake wall "straightens the air" as it flows into the chamber to create laminar, as opposed to turbulent, air flow.

In the middle of the tunnel is a 3-foot-wide opening where the magic happens: a space for a square wooden box, containing about 1,200 pounds of sand and plants that is moved with a Bobcat loader and inserted with necessary effort by a pallet jack. The boxes are blasted with sand for a standardized time and speed and then a highly accurate topographic surface scan is captured from overhead. Once one box is done, the next is inserted for a total of 40 trials.

Here in the belly of the beast, equipment measures and records a 3-D scan of the surface so that researchers can understand how the mounds of sand formed around each plant vary as a function of the plant's shape and distance from neighboring plants. The information is tabulated and recorded on software for later analysis.

The wind tunnel is regulated by a small panel where the researcher can adjust wind speed and other factors. Operators can set the wind speed as high as 27 mph. Once the tunnel is cranked up, the three wide bay doors of the garage must be open to avoid the creation of a vortex, Charbonneau said.

So precise is the scanner that researchers can see measurements down to a grain of sand.  From their observations, they can determine precise morphology and topography of the individual sand mounds and the plants contained, according to Charbonneau.

The conventional theory is that taller, steeper plants ultimately build taller, steeper dunes. Charbonneau is working to quantify and test this largely anecdotal notion. Researchers and dune engineers really don't know how plant morphology influences dune morphology or the rate of growth.

Guided by Charbonneau, high school students from the Marine Academy of Technology and Environmental Science (MATES) last month collected morphology data of the hundreds of donated plants from Pineland's Nursery and Island Beach State Park that were cared for over more than a year at the school. Charbonneau said she has seen substantial interest in the research from students at seven academic institutions.

The plants have to be cut to scan the sand surface below, but in just two weeks since the data collection, new wisps of the hardy coastal plants have reemerged and continue to grow toward the sun. In the wind tunnel, Charbonneau hopes to rerun the tests with continued student involvement on hay-like, over-wintered vegetation if enough grows back before the cold ends their growth season.

The tunnel will remain on-site as a permanent fixture, according to John Biscardi, principal of MATES. Academy students, in addition to researchers with outside projects, eventually will have access to the tunnel to conduct their own experiments.

"We're excited to have this wind tunnel here because it is adaptable for use by students in our MATES program for their own project and research," Biscardi said. "And we are working on curriculum that will specifically utilize it and the research that can be gleaned from it."

Over the last 25 years, as much as 73.2 million cubic yards of sand have been dumped along the New Jersey coastline as a barrier to replenished beaches and to build artificial dunes to protect homes, businesses, boardwalks, and other infrastructure from the Atlantic Ocean. The projects have cost the state and the federal government billions of dollars.

In the months after Hurricane Sandy, the Christie administration vowed to build a fortified dune system along New Jersey's 127-mile coastline, estimated to cost more than $2 billion.  Critics have called the plan an expensive and divisive crusade that has sparked lawsuits in such places as Margate and Long Beach Island, where residents and officials have said thanks, but no thanks.

Charbonneau hopes her research will be used to guide any such dune building. While her team's data has been collected but not yet analyzed, Charbonneau asserts there was no mounding, or dune-building, without the plants — just ripples created in the sand.