Gravel sediment tracing from small torrents to trunk channels using pit-tags method: A case study from the upper Guil catchment (Queyras, French Alps)
Résumé
EGU 2016 Session GM9.1/HS11.15/NH1.24 Mountain streams : processes, channel morphology and knickpoint dynamics (co-organized) 1 Background and scientific context In mountainous areas, especially in large catchments with torrential tributaries, the production and sediment transport signiicantly increase ood impacts in the valley bottoms. The quantiication and characterisation of sedimentary transfers are therefore major challenges to provide better ood risk management. As a part of SAMCO (ANR 12 SENV-0004 SAMCO) project, for mountain hazard assessment in a context of global changes, we tried to improve the knowledge of these hydromorphological systems at both spatial and temporal scales, by identifying sediment supply and sediment dynamics from torrential tributaries to the trunk channel. A sediment budget was used as a tool for quantifying erosion, transport and deposition processes. This research is focused on a part of the sedimentary budget to understand the torrential processes and to deene debris-ow's contribution. It is localized on the Upper Guil catchment, prone to catastrophic ash oods in active channel and alluvial fans. It is characterised by huge sediment transport coming from small torrential tributaries. In this study, we intend to highlight sediment dynamic between small torrential channels and its connection with gravel-bed streams, and characterize the sediment volume mobilized during a large debris-ow event.
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