Transition Indices of Sediment-Transport Modes on a Debris Flow Resulting from Changing Streambed Gradients

We conducted experiments using an experimental flume with two variable streambed gradients in the upstream and downstream parts with various debris flows, composition sizes, and supply flow rates. We investigated the transition processes of sediment transport modes along the longitudinal distances from the gradient change point using the transition mode indices,

I_{\bar{C s} x}

I_{\bar{h} x}

, and

I_{\bar{U} x}

; these indices were calculated based on measurements of sediment transport concentrations, flow depths, and gravel migration velocities in the debris flow’s front in the downstream part. Using these indices, we postulated that after the debris flow passed the gradient change point, the transition of the sediment transport modes progressed by changing the measured parameters to those in the steady-state condition on the gradient of the downstream parts. In addition, these indices suggested that the gravel migration velocities in the flow front interior changed most rapidly after passing the gradient change point, and that flow depths tended to change most slowly. Finally, the indices suggested that as the debris flow material became finer and the supplied flow rates became larger, the longitudinal transition sections tended to be longer because the momentum needed to transport the material was less than the total debris flow momentum. View Full-Text

Keywords: debris flow; sediment transport mode; transition process; changing streambed gradient; sediment transport concentration; flow depth; gravel migration velocity; flume experiment

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Wada, T.; Mishima, H.; Takemura, J.; Kobayashi, K.; Miwa, H. Transition Indices of Sediment-Transport Modes on a Debris Flow Resulting from Changing Streambed Gradients. Water 2022, 14, 1810. https://doi.org/10.3390/w14111810

AMA Style

Wada T, Mishima H, Takemura J, Kobayashi K, Miwa H. Transition Indices of Sediment-Transport Modes on a Debris Flow Resulting from Changing Streambed Gradients. Water. 2022; 14(11):1810. https://doi.org/10.3390/w14111810

Chicago/Turabian Style

Wada, Takashi, Hirotada Mishima, Jin Takemura, Kazuki Kobayashi, and Hiroshi Miwa. 2022. "Transition Indices of Sediment-Transport Modes on a Debris Flow Resulting from Changing Streambed Gradients" Water 14, no. 11: 1810. https://doi.org/10.3390/w14111810

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Transition Indices of Sediment-Transport Modes on a Debris Flow Resulting from Changing Streambed Gradients

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