• DOI:10.1139/E91-030
• Corpus ID: 53312879

How do gravel-bed rivers braid?

@article{Ashmore1991HowDG,
  title={How do gravel-bed rivers braid?},
  author={Peter Ashmore},
  journal={Canadian Journal of Earth Sciences},
  year={1991},
  volume={28},
  pages={326-341}
}

• P. Ashmore
• Published 1 March 1991
• Geology
• Canadian Journal of Earth Sciences

Sedimentary processes and bed forms leading to the onset of braiding were observed in small-scale hydraulic models of gravel-bed streams. The laboratory streams had a variety of combinations of (constant) discharge and slope but identical bed-material particle-size distributions. From initially straight channels, braiding occurred by four different processes: deposition and accumulation of a central bar, chute cutoff of point bars, conversion of single transverse unit bars to mid-channel braid bars, and dissection of multiple bars. In these experiments the chute cutoff mechanism was the most common, but the predominant braiding mechanism depends upon sediment mobility (excess bed shear stress) and the bed-form regime. At very low excess bed shear stress the central bar process dominates, but at higher excess bed shear stress slip-face unit bars are more common, bed scour at confluences is more pronounced, and propogation of alternate convergence (scour) and divergence (deposition) is more likely; thus chu...