Professor Brett Milligan uses drone imaging and photogrammetry to study landscapes. (John Stumbos | UC Davis)
Landscape architecture professor Brett Milligan studies how humans manipulate and design with sediment.
“We are the preeminent geologic agents on earth,” Milligan said. “We move more material than rivers, glaciers, and wind combined. If you look through history, there is this ever-aggregating trend of moving more earth and material around, both deliberately and inadvertently.”
Society has had to get smarter and more creative in working with this material. Ports create tremendous amounts of dredge material to keep shipping channels open and trade flowing. Dredge material from the Stockton shipping channel is being used to rebuild the nearby Antioch Dunes, home to two species of endangered wildflowers and the world’s only population of Lange’s metalmark butterfly.
Milligan is using new tools to understand how the landscape takes shape on the wind-blown dredge sediment, which is mostly sand. “We’re hoping to use drone imaging and photogrammetry to learn how that sand moves over time and how it might optimally be placed and formed to create habitats,” he said.With a drone-mounted, wide-angle camera, Milligan can pinpoint what he wants to see in microscale detail and obtain real-time footage. Sophisticated software can then stitch together the high-resolution imagery for use in 3-D models that run in a geographic information system. The resulting simulations give scientists and managers greater insight into landscape processes.
Milligan also has looked at other dredge sites such as the former Hamilton Air Force Base in Marin County, Calif., where tidal wetlands have been created by building up subsided lands and reconnecting them to the San Pablo Bay.
The drought has created an opportunity to utilize this technology to study California’s reservoirs. With unmanned aerial vehicles and high-resolution photography, researchers are learning how to create bathymetric surveys that might help assess accumulated sediment in the exposed bottoms of reservoirs.
This type of imaging technology also has applications in urban forestry. Milligan recently worked with the Climate Action Reserve to create a protocol for quantifying carbon sequestration in urban trees.
Milligan began using drones in 2014 and has been working with graduate researcher John De Goede to see how they can use the technology in combination with a variety of mapping and modeling software. They are enthusiastic about the wealth of new information this technology can provide. “I think with drones it’s about what you do with the applications,” Milligan said. “From an environmental point of view, this has opened up all sorts of new realms.”