Self-limitation of sand storage in a bedrock-canyon river arising from the interaction of flow and grain size

Journal of Geophysical Research Earth Surface
By: , and 



Bedrock-canyon rivers tend to be supply limited because they are efficient transporters of sediment and not because the upstream supply of sediment is small. A byproduct of this supply limitation is that the finer alluvium stored in these rivers has shorter residence times and smaller volumes than in alluvial rivers. To improve our understanding of disequilibrium sediment transport and its effect on sand storage in bedrock-canyon rivers, we undertook a 20-year study, synthesized herein, of the Colorado River in Grand Canyon. Despite the large loads for which it was renowned, this river exhibited evidence of natural sand-supply limitation and became the perfect natural laboratory for studying sand transport in a bedrock canyon after upstream dam construction exacerbated this supply limitation. During our study, we made and analyzed an unprecedented ∼2.5 million measurements of the suspended and bed sediment. Results indicate that sand storage in this bedrock-canyon river is self-limiting owing to the physical controls of flow and grain size causing negative feedbacks that likely also operate in other bedrock-canyon rivers. Following episodic tributary floods that supply finer sand, sand migrates quickly downstream in the form of a wave in which large systematic changes in bed-sand grain size occur. These grain-size changes cause discharge-independent systematic changes in suspended-sand concentration in excess of a factor of 20. Although the tributary supply of sand increases the amount of sand storage, it also greatly increases the downstream sand transport by causing bed-sand fining, thus limiting the residence time and volume of sand storage.

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Publication type Article
Publication Subtype Journal Article
Title Self-limitation of sand storage in a bedrock-canyon river arising from the interaction of flow and grain size
Series title Journal of Geophysical Research Earth Surface
DOI 10.1029/2020JF005565
Volume 126
Issue 5
Year Published 2021
Language English
Publisher American Geophysical Union
Contributing office(s) Arizona Water Science Center, California Water Science Center, Southwest Biological Science Center
Description e2020JF005565, 37 p.
Country United States
State Arizona
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