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Citation Zimmermann, A. M., Church, M., and Hassan, M. A., 2010. Step-pool stability: testing the jam state hypothesis, Journal of Geophysical Research, 115, F02008, doi:10.1029/2009JF001365.
Organization UBC
URL http://onlinelibrary.wiley.com/store/10.1029/2009JF001365/asset/jgrf662.pdf?v=1&t=ihcwe0lr&s=d1a69001496142c8668b49bde71a9241668e4a6e
Abstract/Description or Keywords We investigate the stability of step‐pool channels by examining how the traditional
approach to bed stability based on the critical Shields number is modified by particles
jamming across the width of the channel. Experiments were conducted in a flume with slopes
ranging between 3% and 18% and either smooth or rough walls. By varying the size of
sediment and width of the flume we observed that the stability of the bed increases as the
jamming ratio (channel width/D84step is the diameter at which 84% of the step stones are
smaller) decreases for jamming ratios less than six. At low jamming ratios both grain‐
on‐grain structuring and sediment entrainment phenomena affect the stability of the bed.
Actual bed failure, however, depends upon the history of bed development and the
chance arrangement of the stone structures in the bed. Thus, the experiments also
demonstrate that the inherently stochastic nature of sediment transport affects not only
the movement of individual grains but also the stability of the channel as a whole. Since
stochastic processes affect the stability of the entire channel, there is no clearly defined
separation between stable and unstable beds, rather, an overlapping field where both stable
and unstable bed states can exist. This field was modeled using logistic regression to
derive a probability of bed failure. A comparison of data from experiments with rough
banks and smooth banks showed that rough banks significantly increase the stability of
the bed.
Information Type article
Regional Watershed Province
Sub-watershed if known
Aquifer #
Comments
Project status complete
Contact Name Marwan Hassan
Contact Email [email protected]