image: View looking down-canyon of Rainbow Canyon showing bottom and steep sidewalls view more
Credit: Image credit: Li Zhang
A study offers insight into how rivers incise tablelands and form canyons over time. Canyons are deep, narrow valleys carved by rivers and characterized by steep slopes. Gary Parker and colleagues developed a morphodynamic model to uncover insights into how rivers incise tablelands and form canyons over time. The authors considered factors including abrasion of the riverbed by sediment and contribution of sediment from upriver alluvial sources and sidewall erosion. The model also included migration of the headwall of the canyon upstream. The headwall represents a type of knickpoint, a change in slope due to differential erosion between the upriver alluvial sediment and the downriver bedrock. The model predicts that alluvial sources are likely to have a lower slope than the bedrock. The authors applied the model to Rainbow Canyon near California's Death Valley and found that, like most canyons, Rainbow Canyon has a shallow slope above the headwall. The model indicates that the difference in slope is inversely proportional to the migration rate of the headwall, suggesting that Rainbow Canyon's headwall took 120,000 years to reach its current position. According to the authors, the model provides a template for predicting long-term canyon incision, sidewall erosion, and canyon extension into the uplands in tectonically active terrain prone to canyon formation.
ARTICLE #19-11040: "How canyons evolve by incision into bedrock: Rainbow Canyon, Death Valley National Park, United States," by Li Zhang et al.
MEDIA CONTACT: Gary Parker, University of Illinois at Urbana-Champaign, Urbana, IL; e-mail: parkerg@illinois.edu
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Journal
Proceedings of the National Academy of Sciences