Using Continuous Turbidity and Seismic Measurements to Unravel Sediment Provenance and Interaction Between Suspended and Bedload Transport in an Alpine Catchment

International audienceStudying sediment transport partitioning between bedload and suspended load has been a major research topic for decades (Bagnold, 1966; Einstein et al., 1940; Turowski et al., 2010). This partitioning is crucial for the understanding of sediment transport processes and the transfer of sediment in catchments. Coarse particles (boulders to sand) are often considered to be transported as bedload by sliding, rolling, or saltating and thus strongly interacting with the river bed and its morphology (Ashmore, 1988; Hoey, 1992). Finer particles (sand to clay) are often considered to be transported over longer distances in suspension throughout the water column without necessarily interacting with the bed (Einstein et al., 1940). Due to these long transport distances, the fine fraction generally originates from various sources and processes including rainfall and runoff erosion of nonvegetated hillslopes (Cheraghi et al., 2016; Mohamadi & Kavian, 2015) or rapid mass movements and debris flows suddenly connecting source areas to the river system (Fryirs, 2013). The fine fraction may also originate directly from the river bed resuspension (Misset, et al., 2019), although the extent to which this fraction interacts with the river bed is often unknown (Walling et al., 1998). Quantifying this is crucial for the understanding of landscape evolution (Ludwig & Probst, 1998), river system, and reservoir management planning (Kondolf et al., 2014) or optimizing water resource qualit