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https://doi.org/10.5194/esurf-2017-46
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
31 Jul 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Earth Surface Dynamics (ESurf).
Alluvial cover controlling the width, slope and sinuosity of bedrock channels
Jens Martin Turowski Helmholtzzentrum Potsdam, German Research Centre for Geosciences GFZ, Telegrafenberg, 14473 Potsdam, Germany
Abstract. The problem of bedrock channel meandering is closely related to the problems of channel width and slope. Active meandering occurs when the channel walls are eroded, which also drives channel widening. Further, for a given drop in elevation, the more sinuous a channel is, the lower is its channel bed slope in comparison to a straight channel. It can thus be expected that studies of bedrock channel meandering give insights into width and slope adjustment and vice versa. The mechanisms by which bedrock channels actively meander have been debated since the beginning of modern geomorphic research in the 19th century, but a final consensus has not been reached. Remote sensing studies of the Pacific Arc islands show that regional channel sinuosity scales with storm frequency and inversely with the erodibility of the substrate. However, no mechanisms are known that effectively reduce sinuosity and keep it at a constant value, and a coherent theoretical explanation for the field observations is lacking. It has long been argued that whether a bedrock channel meanders actively or not is determined by the availability of sediment relative to transport capacity, a notion that has also been demonstrated in laboratory experiments. Here, this idea is taken up by postulating that the rate of change of both width and sinuosity over time is dependent on bed cover only. Based on the physics of erosion by bedload impacts, a scaling argument is developed to link bedrock channel width, slope and sinuosity to sediment supply, discharge and erodibility. It is shown that this simple model built on sediment-flux driven bedrock erosion yields the observed scaling relationships of channel width and slope with discharge and erosion rate, can explain why sinuosity evolves to a steady state value and predict the observed relations between sinuosity, erodibility and storm frequency.

Citation: Turowski, J. M.: Alluvial cover controlling the width, slope and sinuosity of bedrock channels, Earth Surf. Dynam. Discuss., https://doi.org/10.5194/esurf-2017-46, in review, 2017.
Jens Martin Turowski
Jens Martin Turowski
Jens Martin Turowski

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Short summary
Bedrock channels are a key component of mountaineous landscapes. Here, a new model of the steady state morphology, including channel width, slope and sinuosity, is derived from process physics considerations. The model compares favourably to observed scaling relations.
Bedrock channels are a key component of mountaineous landscapes. Here, a new model of the steady...
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