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Spatial and temporal dynamics of suspended sediment fluxes in an alpine river: the Arc and Isère rivers, France
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  • Benoit Camenen,
  • Julie Archambault,
  • Fabien Thollet,
  • Christophe Rousseau,
  • Julien Némery
Benoit Camenen
IRSTEA Lyon

Corresponding Author:[email protected]

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Julie Archambault
Irstea
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Fabien Thollet
Irstea
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Christophe Rousseau
INP Grenoble
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Julien Némery
INP Grenoble
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Abstract

Fine sediment dynamics is an important issue in alpine rivers since it impacts both dam management (decrease of the reservoir capacity, flushing strategy) and river management (interaction between fine sediment and vegetation, gravel bar stabilisation, flood risk). Suspended Particle Matter (SPM) is generally assumed to be transported as washload although significant exchanges with the river bed have been detected in several cases. As a consequence but also due to the variable SPM sources and differences in the discharge and sediment wave velocities, one can often observe a hysteresis behaviour during hydrological events that evolves spatially along the system. In this study, we will present results from a network of hydro-sedimentary stations (measuring both water discharge and sediment concentration) along a reach of 120 km starting from the Arvan River at its confluence and the Arc and Isère rivers, that is part of the ZABR (or Rhône Basin Long Term Environmental Research Observatory). The SPM dynamics is analysed for different types of events (large flood, spring flood, flushing event, debris flow). In particular, we focus on the potential of erosion or deposition between each station by calculating the total SPM flux during each event at each station as well as the hysteresis behaviour using a hysteresis index. The evolution of these parameters is related to input parameters such as discharge and sources and grain size characteristics of the suspension. Indeed, most observed sediment exchanges (erosion or deposition) occur on the gravel bars when inundated, and depend on settling characteristics of the SPM. Also the experimental site provides some useful data for estimating advection and dispersion characteristics of various SPM events that could be used to validate numerical models.