Geophysical Research Letters

Processes of initiation of motion leading to bedload transport in gravel-bed rivers

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Abstract

[1] Transport processes that lead to the initiation of bedload motion in gravel-bed rivers have not yet been clarified. We report patch- and grain-scale processes involved in the initiation of bedload motion in a natural gravel-bed stream as observed through a series of video experiments. With increasing flow strength, the phases of initiation of motion that have been identified are (1) within-patch grain instability (grain vibration, pivoting, and grain-scale rolling), (2) within-patch gyratory step-and-rest motion, and (3) general sediment motion involving downstream transport from an individual patch and the throughput of grains inherited from upstream.

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