A recent set of four related articles published in the Journal of Geophysical Research-Earth Surface takes a new approach to understanding sediment transport, a vital component to the ecological health and long-term evolution of river channels.
When you look at a river’s water surface, it is rarely smooth. Instead, you can usually see the continual churning of turbulent river flow. Sediment transport occurs as this turbulent flow disturbs sand and gravel riverbeds, and the river is flowing fast enough to move the particles downstream. The complex nature of turbulent river flow makes quantifying sediment transport a difficult task.
The new approach to understanding sediment transport developed in this study involves describing individual sediment particle motions and positions as the basis for calculating total transport amounts. High-speed videos of sand grains moving at different flow rates were analyzed to provide experimental data to compare with the new theory. A video showing digitized sand grains transported during experiments is available here. The transport of sand particles is shown by experiment results to be extremely variable in both the location and amount of sediment movement at any given flow. This variability in particle motions results from the complex interaction of turbulent flow with the riverbed.
As our understanding of sediment transport and other river processes continues to improve, so does the ability of the restoration community to provide effective, science-based solutions to degraded aquatic resources, increasing the likelihood of long-term success of restoration projects.
Author John Roseberry, an Environmental Engineer at Trout Headwaters, Inc. and Ph.D. candidate at Vanderbilt University, was lead author of the second article in the series of four from this study.
Roseberry et al, 2012: http://www.agu.org/pubs/crossref/2012/2012JF002353.shtml
Furbish et al, 2012a: http://www.agu.org/pubs/crossref/2012/2012JF002352.shtml