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Multi-site comparison of gravel travel distance by RFID tracking in large rivers: methodological and practical feedback. Comparaison multi-sites des distances de déplacement des graviers par suivi RFID en grandes rivières : retour d'expérience méthodologique et pratique
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Edité par CCSD -
International audience. The hydro-sedimentary processes of the Rhône River have been severely altered by human activities since the 19th century, notably through the construction of groyne fields and diversion dams, which has caused a loss of in-stream habitat and biodiversity. In this context, several restoration actions have been implemented to mitigate this physical effect (i.e., gravel augmentation, groyne fields removal to promote bank re-erosion and sediment supply). In order to evaluate the efficiency of these operations and better understand the sediment transport of the Rhône River and the effect of a diversion dam on bedload continuity, gravel mobility was assessed by particle tracking using RFID-technology at 5 sites located along 322 km. Thus, nearly 4700 tagged pebbles were deployed between 2016 and 2019 (4400 PIT and 300 u-UHF tags) and their location surveyed 2 to 5 times over a period of 1.5 to 6 years, depending on the site. The results are presented at two scales. At the river scale, the 5 sites, which differ according to their natural setting and human impacts, are compared in term of travel distances and virtual velocities. At the reach scale, the comparison of local virtual velocities highlights large differences (one order of magnitude) between the different parts of the channel (main thalweg, gravel bar and side channel). This study provides methodological results for applying such technique in a multi-site context to large non-wadable rivers (i.e., decrease in recovery rates over time, suitability of tracer types and sizes) and recommendations for monitoring and evaluating restoration actions.
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