Fluvial Geomorphology and Dam Failure Analysis Utilizing NASA’s Surface Water and Ocean Topography (SWOT) Satellite

     NASA launched the Surface Water and Ocean Topography (SWOT) satellite in 2022. The satellite is being used to determine the height and extent of bodies of water and how they shape the land. This can be a new way to do fluvial (river) geomorphology. Phys.org writes:

“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.”

     Virginia Tech geoscientists demonstrated that the satellite can be used for fluvial morphology.

"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."

     Three applications include the study of large river dynamics, sharp breaks and slopes along a river, such as waterfalls, and shear stress, which helps scientists to understand how much sediment water pushes along.

     The researchers also demonstrated that SWOT can be used to observe and track dam failures. Aging infrastructure and flooding are often the causes of dam failures.

     SWOT includes an interferometric synthetic aperture radar (inSAR) instrument. InSAR has proven useful for measuring even very small land movements.

     Satellite remote sensing has long been applied to the study of fluvial geomorphology. More recently, it has been applied to study river systems at large scales, something traditional fluvial geomorphology methods can’t do. A paper, published in the Geological Society of America’s GSA Today, explains the advantages:

“The Surface Water and Ocean Topography (SWOT) satellite, launched in December 2022, has the potential to transform the field of fluvial geomorphology by providing new data that are unlike what past satellite missions have offered. SWOT produces high-precision images of surface water topography, enabling a new suite of analyses in fluvial geomorphology. SWOT was primarily designed for oceanography and inland hydrology applications and uses a Ka-band synthetic aperture radar to provide simultaneous measurements of both the elevation and extent of surface water over two 50-km-wide swaths (Fu et al., 2024). These same observations can also be readily utilized for fluvial geomorphology applications. The measured water surface elevation (WSE) is an important geomorphic variable in itself, and it can be used to estimate other variables including river slope and river discharge, both of which are related to sediment transport processes (Wolman and Miller, 1960; Bagnold, 1966; Howard et al., 1994).”

     These new methods complement other techniques such as light detection and ranging (LiDAR). Data can be presented in three formats: vector, raster, and pixel cloud (a point cloud of water mask pixels).

     The paper goes on to show how SWOT can be used to study large river dynamics, bed shear stress, and knick points. Large river systems are more complex and harder to study.

“…they often have greater internal complexity, more anabranching, and a wider range of channel planforms (Ashworth and Lewin, 2012). These complexities can make predicting their geomorphic behavior difficult, and much work has been dedicated to modeling and quantifying the morphology of large and braided rivers (Williams et al., 2016).”

     Below is a SWOT analysis of the Yukon River in Alaska.

     Channel bed shear stress, a fundamental measure of a river’s ability to move bed material, can be used to study sediment transport.

“Figure 3 shows an example of shear stress calculations along the Klamath River in northern California using the SWOT RiverSP node product. The Klamath River is currently a site of great interest due to the ongoing removal of a series of dams along its upper reaches.”

     Knickpoints are abrupt increases in downstream slope along a channel profile, such as at a waterfall. Knickpoints in streams migrate, and SWOT can be used to better measure migration rates. Dam removals and other landscape and water changes can create new knickpoints. SWOT can be used to predict knickpoint migration after dam removals.

“Forecasting the effects of dam removal (or failure) is challenging, but new data from SWOT will allow us to study the postevent knickpoint migration and channel morphology change, improving our understanding of the geomorphic effects of dam removal (Pizzuto, 2002). Additionally, we now have the capability to directly observe and measure knickpoint and knick-zone migration rates at a global scale and at regular temporal intervals.”

     Below is an analysis of the Rapidan Dam on the Blue Earth River in Minnesota, before and after dam removal.

     The authors think that SWOT will be used for other fluvial geomorphology applications as well and lead to more accurate databases of river dynamics. The geomorphic impacts of floods can be studied with SWOT as well. The long-term effects of both dam construction and dam removal using the satellite can be determined more accurately than before. SWOT data can also be used to improve modeling and simulations.  

 

 

   

References:

 

Geoscientists use satellite data to determine how water shapes the land. Kelly Izlar. Phys.org. January 19, 2026. Geoscientists use satellite data to determine how water shapes the land

SWOT Satellite: A New Tool for Fluvial Geomorphology. Molly Stroud, George H. Allen, J. Toby Minear. Julia Cisneros, and Laurence C. Smith. Geological Society of America. GSA Today. Volume 35 Issue 12 (December 2025). SWOT Satellite: A New Tool for Fluvial Geomorphology