Processes of deposition and erosion of fine sediments
Gravel bars constitute an important storage for fine sediments that is still poorly understood (Marttila & Klove, 2014). The main issue will be to characterize fine sediment dynamics (erosion and deposition) at the scale of a small reach (including one or several gravel bars) and during non-steady conditions (Figure 5). In particular, a differentiation will be made between sediments available over gravel bars (surface deposits) and sediments available within the bed matrix (infiltrated fine particles) since their resuspension is run by different physics, i.e direct erosion by the flow or resuspension linked to interstitial flows or gravel movement initiation. As the storage duration might be very different for the two different types of stock, these fundamental issues need to be handled to assess the range of transit times of fine sediments in alpine rivers as well as the potential impact of fine sediments on gravel bar fixing and/or on the development of vegetation (Jourdain et al., 2017).
This workpackage is divided into 3 subtasks:
2.1. Surface deposit dynamics
2.2. Fine sediments trapped in the bed matrix: exchange with the flow
2.3. 2DH modelling