Impacts of Suspended Clay Particle Deposition on Sand-Bed Morphodynamics

J. Dallmann*, C. B. Phillips, Y. Teitelbaum, N. Sund, R. Schumer, S. Arnon, A. I. Packman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Fine particles (0.1–100 microns) are ubiquitous within the water column. Observations on the interactions between suspended fine particles and sediment beds remain limited, reducing our ability to understand the interactions and feedbacks between fine particles, morphodynamics, and hyporheic flow. We performed laboratory experiments to explore changes in bedform morphodynamics and hyporheic flow following the progressive addition of kaolinite clay to the water column above a mobile sand bed. We characterized these interactions by taking high-frequency time series measurements of bed topography and freestream clay concentration combined with solute injections and bed sediment cores to characterize subsurface properties. Deposition of initially suspended clay resulted in a decrease of bedform height, celerity, and sediment flux by 14%, 22%, and 29% when 1000 g was accumulated within the bed (equal to clay/sand mass ratio of 0.4% in the bed). The hyporheic exchange flux decreased by almost a factor of 2 for all clay additions, regardless of the amount of clay eventually deposited in the bed. Post experiment sediment cores showed clay accumulation within and below the mobile layer of the bedforms, with the peak concentration occurring at the most frequent bedform scour depth. These results demonstrate the tight coupling between bed sediment morphodynamics, fine particle (clay) deposition, and hyporheic exchange. Suspended and bed load transport rates are diminished by the transfer of suspended load to the sediment via hyporheic exchange. This coupling should be considered when estimating sediment transport rates.

Original languageEnglish (US)
Article numbere2019WR027010
JournalWater Resources Research
Volume56
Issue number8
DOIs
StatePublished - Aug 1 2020

Keywords

  • Cohesion
  • Fine Particles
  • Hyporheic Exchange
  • Mobile Bedforms
  • Sand-Bed
  • Sediment Transport

ASJC Scopus subject areas

  • Water Science and Technology

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