Geoscientists use satellite to determine not the shape of water, but how water shapes land

What’s the shape of water?

In 2022, NASA launched the Surface Water and Ocean Topography (SWOT) satellite to answer this question by precisely measuring the height and extent of bodies of water.

Virginia Tech geoscientists are using the same satellite to ask a related question: How is water shaping the land?

“We wanted to show how the satellite could be used in ways that it wasn't primarily designed for,” said postdoctoral associate Molly Stroud, first author of a recent publication in the Geological Society of America Today. “How are rivers and streams moving sediment and shaping the Earth's surface?”

Stroud’s question happens to be the main objective of an entire scientific field known as fluvial geomorphology.

“I don't think it was any secret that SWOT could probably be used for fluvial geomorphology, but the great potential of the satellite wasn’t on the radar for much of that community,” said George Allen, associate professor in geosciences. “The purpose of this paper was to say, hey, look, there's this great new tool that can be used to do brand new things in this field.”

In the past, fluvial geomorphologists relied on airborne surveys or fieldwork in which they carefully studied a single location. Researchers would map out river cross sections to estimate things like how much sediment a river can carry away and how likely a river is to flood in different conditions.

All this just got a lot easier, thanks to Virginia Tech’s demonstration of the SWOT satellite’s versatile technology.

“SWOT allows us to cover all the rivers in the world and understand how they're evolving,” said Stroud. “It really transforms the scale at which we can study rivers.”

To showcase the satellite’s capability, the study looked at three applications:

1. Large river dynamics
2. Sharp breaks and slopes along a river, such as waterfalls
3. Shear stress, which helps scientists to understand how much sediment water pushes along

The team of researchers, which included Julia Cisneros of the Department of Geosciences and collaborators at the University of Colorado and Brown University, also investigated how SWOT can be used to observe and track dam failures, which are exacerbated by aging infrastructure and more frequent and intense flooding.

There are thousands of dams across the U.S.; no one can say exactly when a dam will fail or the long-term effects a failure will have on rivers or the ecological communities they support.

“As SWOT accumulates a longer record, we'll be able to get a better understanding of questions like these and others in the field of fluvial geomorphology,” Stroud said.

But for now, they’re just getting their feet wet.

Original study DOI: 10.1130/GSATG630A.1