As organizations around the world work to better understand the benefits that natural infrastructure can provide both people and the environment, IRIS researchers are doing on-the-ground work to estimate the ecological benefits of a method touted for its benefits both up- and downstream: the levee setback.

While traditional levees are walls or embankments placed alongside rivers to prevent flooding, levee setbacks are simply levees that have been moved further away from the river, widening the river’s floodplain and allowing more space for waters to rise.

By allowing rising waters to spill over the riverbanks, floods are less likely to breach levees and affect communities nearby–as project lead Charles van Rees, Odum School of Ecology, describes it, “loosening the straitjacket” on overflowing riverbanks.

“They are restoring the hydrology, which can change the substrate of the floodplain and the plant communities, which means that it can affect all the terrestrial organisms that live there as well as the ones in the river,” van Rees explained. 

Although it is commonly believed that levee setbacks would positively benefit the species and biodiversity of  their floodplains, it’s unclear if there is real data to support this idea. However, van Rees suspects this is just a lack of examples: “Even though there are more and more levee setback projects, very few of them have been monitored specifically for biodiversity. We know we have very strong reason to believe that there would be these really big systematic changes in the floodplain ecosystems, but the amount of full-on evidence we have is kind of piecemeal.” 

Thanks to support from NASA’s Biological Diversity and Ecological Conservation program,, a project team that includes collaborators across UGA, the U.S. Army Corps of Engineers, and the University of South Dakota are on the ground investigating levee setbacks to learn about real-world biodiversity benefits and fill this knowledge gap.

Levee setbacks in the wild

The levee setbacks that the team are collecting data from are along the lower Missouri River, a major tributary to the even more massive Mississippi River and what van Rees described as a “temperamental” river. The headwaters of the Missouri are largely fed by snowfall in the Rocky Mountains, so pulses in water supply are seasonal, with higher flood frequency in late spring and early summer as the mountain snow melts. This occasionally results in less-than-ideal field conditions.

“We went out to do research last spring, and didn’t see any rain, but suddenly got word that the river was about to go up by 18 feet. We just had to skedaddle,” van Rees laughed. “And then the river did go up by 18 feet, flooding all kinds of stuff… including some of our research equipment.”

But despite the river’s dramatic personality, the lower Missouri is lined by major urban centers like Omaha and St. Louis, with much of the river being hydrologically modified for the safety of the surrounding communities. There have been a handful of levee setbacks in the region, with more planned for the future, so this research team has an interesting opportunity for a massive experiment to see what happens to biodiversity before, during and after a levee setback.

The group started by collaborating on a baseline monitoring system to determine what types of vegetation exist in these habitats and how they’re changing over time. This work is supported by a large grant from NASA, awarded in late 2023 as a grant through the Research Opportunities in Space and Earth Science (ROSES) program.

Additional contributors span across campus in UGA’s Department of Geography and Odum School of Ecology: Deepak Mishra, Director of the UGA Small Satellite Research Laboratory, and project postdoctoral associate Rabindra Parajuli, and River Basin Center Director of Science Seth Wenger are working to associate satellite images with the vegetation and habitat types on the ground. These will be used in conjunction with hydrological and hydraulic models created by IRIS alum Roderick Lammers and research scientist Matt Chambers, which predict watershed dynamics, to model how ecosystems may change in the future.

“We run the levee setback design through these models, figure out how the habitats will change,” van Rees explained. “Once we know what those habitats are, we can guess what sorts of animals are going to show up–and that gets into all the work we’re doing with frogs, birds and bats.”

Taking a closer listen

Another part of the NASA proposal was the use of automated recording units (ARUs) to collect audio, preset to listen for wildlife activity: “recording for birds at dawn and dusk, singing frogs and toads in the middle of the night, and listening for bats at night using hypersonic equipment.”

Using these recordings, the team is utilizing Cornell University’s BirdNet AI software to identify the species heard in each recording. This data is planned for at least three student projects, starting with Natural Infrastructure Fellow Aurora Fowler, who will be analyzing the frog and toad data (a group known as anurans). 

“Frogs and toads are good indicators of high quality habitat for a wide variety of critters,” Fowler said. “In addition to the birds and bats that we’re recording, I’m investigating anuran response to levee setbacks by seeing where these animals are and what their habitat is like.”

This summer, Fowler set out on a field trip to collect the in-person data needed to learn more about the wildlife in these sites. Armed with nets for catching tadpoles and equipment for reading water quality data, this Natural Infrastructure Fellow will assess key habitat variables like water quality, habitat quality, and the presence of anuran predators, while future students will do the same for the bird and bat recordings the team collects.

These efforts are all ultimately to help the U.S. Army Corps of Engineers, one of the largest organizations in the country doing infrastructure and ecosystem restoration projects, make more informed decisions.

“We plan to develop a pair of predictive AI models that can estimate what types of habitats and what types of animal communities we’re expecting to see on the floodplains when they’re restored,” van Rees explained. “The goal is to help the Army Corps measure the benefits of levee setbacks more effectively. We don’t want to leave benefits on the table.”

To follow along with this work as it continues to develop, check out our project page here or through van Rees’s Wildlife and Water Lab.

Image by Aurora Fowler.