Environmental researchers use drones to map marshes
Restoration has begun to preserve the sites that reduce flooding and prevent erosion along Currituck Sound.
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This past summer, researchers from the Carolina Drone Lab — a collaborative research unit within the UNC Institute for the Environment — visited four marsh sites along the Currituck Sound as part of a study on the applications of drone technologies for coastal resilience and habitat monitoring.
They are partnering with Elizabeth City State University and Audubon of North Carolina to aid in understanding the status of the marshes and the future management of the sound. The North Carolina Collaboratory and the Slick Family Foundation funded the project.
“Our partnerships are very important,” says Troy Walton, senior research associate in the UNC Institute for the Environment. “ECSU has a great aviation program and a wide variety of drones, which allows us to have another data set for comparison. Audubon owns the property that we’re collecting on, and they’re leading the restoration efforts.”
The research team records data from the marsh. (Megan Mendenhall/UNC Research)
High-tech conservation
Marshes are important for many reasons. They help to reduce the impact of flooding in coastal communities by absorbing and storing excess water. They filter water and prevent erosion. And they provide a habitat for a variety of wildlife, especially waterfowl, which draw tourists to the Currituck Sound each year, supporting the local economy.
But the sound is changing drastically. Nearly 72 acres of marshes in Currituck County are lost every year due to the combined effects of erosion and sea-level rise.
“If nothing happens, that marsh is going to end up drowning in the very near future,” Walton says.
To help protect and revive marsh habitat, Audubon of North Carolina began a series of sediment restoration pilot projects at the Donal C. O’Brien Jr. Sanctuary and Audubon Center at Pine Island. They dredge sediment from the sound and apply it to the marsh surface to elevate the land.
Satellite imagery can show the overall trajectories of marsh erosion and movement, but often with poor resolution and incorrect scales.
This is where the Carolina Drone Lab comes in. By stitching together over 1,000 super-high resolution drone photos, Walton and his team can create an image of the marsh with centimeter accuracy.
They also use the data to create a digital surface model that shows the elevation across the marsh and to understand if the elevation of the marsh is keeping up with local sea-level rise. Then, they compare that data with elevation points collected on the ground using a handheld GPS unit to verify its accuracy.
“This research benefits the citizens of North Carolina because the marsh problem is not just localized to Currituck Sound — it is across North Carolina and the world,” Walton says. “If we can better understand what’s happening here, then we’re able to take these strategies and expand them to the state and then hopefully further beyond that as well.”
“The sediments in the Currituck are really squishy [and] slimy,” says Peggy Mullin, a UNC-Chapel Hill master’s student. “Getting stuck in the marshes is just part of the job.”
Impact of underwater plants
While the larger project in the sound is focused on sediment, Peggy Mullin — a master’s student in the environment, ecology and energy program in the College of Arts and Sciences — wants to know how underwater plant life affects the marsh.
A vital component of aquatic ecosystems, this plant life provides habitats for fish, invertebrates and other marine organisms, while also improving water quality by absorbing excess nutrients. Additionally, its roots can stabilize sediments, reducing erosion.
For her investigation, she pilots a drone equipped with a specialized camera to detect the underwater plants. Then she goes out into the marsh to observe the vegetation there. She wants to determine if remote sensing tools are useful to detect and monitor the underwater plants.
“Once we figure out whether or not that can be done, that will have a lot of impacts on coastal monitoring and for the future of North Carolina’s coasts,” she says.
