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Research Articles: Fluvial Sedimentation |
1 Earth and Biosphere Institute, School of Earth and Environment, University of Leeds, West Yorkshire, LS2 9JT, U.K.; j.peakall{at}earth.leeds.ac.uk
2 Division of Geography, School of the Environment, University of Brighton, Sussex, BN2 4GJ, U.K.
3 Earth and Biosphere Institute, School of Earth and Environment, University of Leeds, West Yorkshire, LS2 9JT, U.K.
Realistic physical models of meandering rivers have proven extremely difficult to produce, particularly in comparison to the formation of braided rivers in the laboratory. Here we address the question of why such realistic model meanders are so difficult to reproduce, through the most realistic physical modeling of meandering channels yet achieved. This paper demonstrates that cohesion is a key variable in the development and maintenance of single-thread channels. In particular, cohesion must be sufficient to force the planform away from a braided state but low enough for active migration to continue and for the avoidance of a gradual reduction and eventual cessation of planform movement (ossification). The enhanced realism of the experiments also enables the processes of meander evolution, and critically the resultant alluvial architecture, to be examined in a physical model for the first time. Planform history can be linked to deposits, and this process–product linkage enables the depositional development of the experimental deposits to be compared against, and to test, existing models of bedding geometries within point bars. Here we document three mechanisms for bend cutoff, provide new process explanations for certain modes of bend evolution in coarse-grained meandering rivers, examine the geometries and spatial distribution of alluvial architecture, and demonstrate that existing models of point-bar geometry successfully reproduce the larger-scale aspects of point-bar accretion in rivers dominated by episodic unit-bar accretion.
This article has been cited by other articles:
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  T. Nakajima, J. Peakall, W. D. McCaffrey, D. A. Paton, and P. J. P. Thompson Outer-Bank Bars: A New Intra-Channel Architectural Element within Sinuous Submarine Slope Channels Journal of Sedimentary Research, December 1, 2009; 79(12): 872 - 886. [Abstract] [Full Text] [PDF]
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 A. D. Howard How to make a meandering river PNAS, October 13, 2009; 106(41): 17245 - 17246. [Full Text] [PDF]
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C. A. Braudrick, W. E. Dietrich, G. T. Leverich, and L. S. Sklar Experimental evidence for the conditions necessary to sustain meandering in coarse-bedded rivers PNAS, October 6, 2009; 106(40): 16936 - 16941. [Abstract] [Full Text] [PDF]
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 I. A. Kane, W. D. McCaffrey, and J. Peakall Controls on sinuosity evolution within submarine channels Geology, April 1, 2008; 36(4): 287 - 290. [Abstract] [Full Text] [PDF]
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