Sediment mobility and bedload transport conditions in an alpine stream |
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Authors: | Luca Mao Mario Aristide Lenzi |
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Institution: | Department of Land and Agroforest Environments, Università di Padova, Agripolis, Viale dell'Università 16, 35020 Legnaro (Padova), Italy |
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Abstract: | The mobility conditions of bedload transport in an alpine high‐gradient step–pool stream (Rio Cordon) are analysed. Since 1986, a device system at the downstream end section of the stream has been operating in order to monitor the water discharge, suspended sediment and bedload transport. Sediment distribution of bedload transported by various floods has been analysed, and equal‐mobility evidence is recognized only for the high‐magnitude flows ever recorded (RI > 50 years). The thresholds for size‐selective and equal‐mobility transport conditions are identified and quantified by using both data provided by the fractional transport rate and by length displacements of marked particles. Size‐selective bedload transport seems to dominate when the critical shear stress of the size fractions τci considered is exceeded, whereas the equal‐mobility condition is approached as levels of excess shear stress become higher (τeqi = 1·45τci). Copyright © 2006 John Wiley & Sons, Ltd. |
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Keywords: | bedload equal mobility size‐selective transport sediment mobility scaled fractional transport step– pool channel |
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