Drones help monitor restoration of Elkhorn Slough wetlands
Research along the brackish waters of Elkhorn Slough, with its extensive tidal salt marsh and meandering seven-mile waterway, has historically required scientists to put on waders and wetsuits or hop aboard a boat. But these days, algorithms and aerodynamics are helping researchers capture a birds-eye view of the estuary from the comfort of shore.
“It’s a really important habitat,” said Dr. Corey Garza, a professor with the Marine Science Department at CSU Monterey Bay. “It supports a lot of different fisheries and overwintering birds.”
The Elkhorn Slough National Estuarine Research Reserve is California’s second largest estuary, second only to the San Francisco Bay. Like the Golden Gate, its waters and wetlands are home to thousands of fish, birds and mammals. In 2018, the Elkhorn Slough was designated a “Wetland of International Importance.”
Using images captured from drones equipped with high-resolution cameras, researchers at Elkhorn Slough are piecing together a picture of how humans have shaped the land over the last century, and how best to restore it.
On a sunny morning in late October, Garza and a handful of marine scientists converged on an area near the slough called the Hester Marsh Restoration site. The overwhelming smell of a nearby dairy is a reminder that these important wetlands were once damaged by agriculture and other human activities. Professor Garza and the other scientists are working on a project to reverse the last century of human-caused damage.
“They've already actually cleared this area to get it ready for restoration,” Garza said. “And so we're doing all the ‘before images’ for them.”
The images are taken from above using small camera-equipped drones to map the restoration site.
Pat Iampietro is the geospatial tech officer and drone coordinator at CSU Monterey Bay. Inside his SUV are cases containing the aircraft, and the other equipment necessary to fly them — ground controllers and waypoints that use satellite geopositioning to define the boundaries of the flight pattern.
“They're flying and taking pictures with very precise positions, so they have a little more setup. So that can be a little quirky,” Iampietro said.
Quirky indeed — the set up takes almost as long as the flights. There are long waits for connections and downloads, some trial and error, then new connections and new downloads.
Finally, the propellers of the small drone begin to twitch and Iampietro shouts a warning. The drone, named “Rogue One” after the Star Wars movie, rises about four feet, hovers a few seconds, and then shoots skyward like a rocket.
It levels off at about 150 feet and then begins its back and forth sweep over the restoration area.
“It's kind of like a Roomba or something,” Iampietro said. “It flies its flight plan that's been given and takes pictures along the way.”
The 1,500 images captured during its flight will produce a 3D photo mosaic that is accurate to within a few centimeters.
Three weeks later and a short distance away, Monique Fountain, the director of the tideland wetlands program at the reserve, studies the detailed maps produced by the drone flights. They fill her laptop with splotches of color, giving it the appearance of a modern art painting. The drone-produced map allows her to track the progress of the estuary’s restoration down to the tiniest detail. She notes the miniscule changes to the estuary’s topography as its contours are reestablished.
“So this has about 10 different colors in here, and each of these colors represent about four millimeters of elevation change,” Fountain explained. “So you can really see in fine detail the change over time.”
Fountain said the team is about two-thirds of the way toward restoring the 1,700 acres that make up the reserve. Between planting native species and adding fresh soil, the construction part of the restoration should be completed next year.
But that doesn’t mean the project is done.
“It will take maybe five or 10 years for the marsh to grow back in,” Fountain said. “So in the end, our hope is that the wildlife move back and the plants move back in and the otters move back and that we have a rich ecosystem again.”
And thanks to drone technology, it's an ecosystem scientists can monitor from above.