Published July 25, 2022 by Jane Godiner ’23

Evan Dethier's River Research Hits Science Magazine

In late June, Science published faculty member Evan Dethier's co-authored research paper, "Rapid changes to global river suspended sediment flux by humans."

Map from Evan Dethier's research paper
A map from Dethier's paper illustrating the variations of suspended sediment concentration over the decades, on an international scale.

The academic research of Dethier, a visiting assistant professor of earth and oceanographic science, reflects his interest in the impact humans have on water resources. His most recent paper is no exception.

"Water is obviously critical to all sorts of animal and plant existence, but it can also pose a threat to us and we can rely on it in ways that end up harming us, and so I think about all of those different intersections," Dethier said in an interview. "In this paper in particular, what we were trying to think about was, over the last forty-ish years, how has the way that rivers transport sediment changed due to human activity?"

Dethier and his team observed these changes by measuring suspended sediment concentration (SSC) and flux.

"[The measure of SSC] basically is, does the river look muddy, or does it not?" Dethier explained. "Most people probably don't think too much about how much sediment is going down the river, but it's actually quite important for lots of different things."

Some of his desire to research this specific topic was triggered by contemporary natural disasters.

"I originally started this work in 2016 in New England during my PhD at Dartmouth, and I was trying to think about how to contextualize this big flood due to Hurricane Irene that we had in 2011," Dethier said. "It was, at the time, a cultural moment and also a really big financial moment, so I was trying to get a sense of how the amount of sediment that was mobilized by rivers during Irene fit into the long-term picture."

His team was able to chronicle the changes in SCC through satellite imaging, which was both exciting and challenging for Dethier.

"The records that we use go back to 1984, because that was the start of this great satellite program run by NASA called the Landsat Missions," he said. "It's really amazing to be able to look back in time and look at some of these images and see how things have changed, but I also had to take that visual impression [and quantify] how things have changed."

Ultimately, Dethier believes his research reveals something of the profound impact that humans have on natural water resources.

"We found that other factors impact SSC, but that human activity is the primary driver of direct change in how much sediment these rivers are carrying," Dethier said. 

Dethier invites interested students to read the complete paper here, and to contact him at e.dethier@bowdoin.edu to learn more about and get involved in his research.

"I work with students from a range of backgrounds and interests," he said. "I'm always looking to incorporate more people into this work."