Coarser and rougher: Effects of fine gravel pulses on experimental step-pool channel morphodynamics

J. P.L. Johnson, A. C. Aronovitz, W. Kim

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Understanding how steep mountain rivers respond to natural and anthropogenic sediment supply perturbations is important for predicting effects of extreme events (e.g., floods and landslides) and for restoring rivers to more natural conditions. Using flume experiments, we show that stabilized step-pool-like channel beds can respond to pulses of finer gravel by becoming even coarser and rougher than before. Adding finer gravel initially reduces bed roughness and also increases the mobility of previously stable bed grains. Small- and intermediate-diameter clasts are then preferentially winnowed from the bed surface, leaving behind higher concentrations of even larger clasts. Ultimately, this results in both a coarser and rougher bed. Our experiments demonstrate that steep river beds become stable through the coevolution of bed roughness and surface grain size distribution and that these morphological variables can be sensitive to the history of upstream sediment supply. Key Points Fine gravel pulses can mobilize coarser bed surface grains Fine gravel pulses can coarsen and roughen mountain river beds The history of sediment supply influences stable bed morphology

Original languageEnglish
Pages (from-to)8432-8440
Number of pages9
JournalGeophysical Research Letters
Volume42
Issue number20
DOIs
Publication statusPublished - 2015 Oct 28

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All Science Journal Classification (ASJC) codes

  • Geophysics
  • Earth and Planetary Sciences(all)

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