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Hydrological drivers of bedload transport in an Alpine watershed
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  • Gilles Antoniazza,
  • Tobias Nicollier,
  • Stefan Boss,
  • François Mettra,
  • Alexandre Badoux,
  • Bettina Schaefli,
  • Dieter Rickenmann,
  • Stuart N Lane
Gilles Antoniazza
University of Lausanne

Corresponding Author:[email protected]

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Tobias Nicollier
WSL
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Stefan Boss
WSL
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François Mettra
Ecole Polytechnique Federale de Lausanne
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Alexandre Badoux
WSL
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Bettina Schaefli
UNIL
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Dieter Rickenmann
WSL
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Stuart N Lane
Université de Lausanne
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Abstract

Understanding and predicting bedload transport is an important element of watershed management. Yet, predictions of bedload remain uncertain up to several order(s) of magnitude. In this contribution, we use a five-year continuous time-series of streamflow and bedload transport monitoring in a 13.4 km2 snow-dominated Alpine watershed in the Western Swiss Alps to investigate the hydrological drivers of bedload transport. Following a calibration of the bedload sensors, and a quantification of the hydraulic forcing of streamflow upon bedload, a hydrological analysis is performed to identify daily flow hydrographs influenced by different hydrological drivers: rainfall, snow-melt, and mixed rain and snow-melt events. We then quantify their respective contribution to bedload transport. Results emphasize the importance of mixed rainfall and snow-melt events, for both annual bedload volumes (77% in average) and peaks in bedload transport rate. Results further show that a substantial amount of bedload transport may occur during late summer and autumn storms, once the snow-melt contribution and baseflow have significantly decreased (9% of the annual volume in average). Although rainfall-driven changes in flow hydrograph are responsible for a large majority of the annual bedload volumes (86% in average), the identified melt-only events also represents a non-negligible contribution (14 % in average). Through a better understanding of the bedload magnitude-frequency under different hydrological conditions, the results of this study may help to improve current predictions of bedload transport, and we further discuss how bedload could evolve under a changing climate through its effects on Alpine watershed hydrology.
Mar 2022Published in Water Resources Research volume 58 issue 3. 10.1029/2021WR030663