Junjian DENG (2019-2022)
PhD student in numerical modelling of fine sediment dynamics
Supervisor: Benoît Camenen (Irstea Lyon)
Doctoral school : MEGA (Mechanics, Energetics, Civil Enginnering, Acoustics), Lyon

Influence of fine sediments on the morphodynamics of an alternate gravel bar system in a harnessed mountain river

The objective of this PhD work is to better understand the fine sediment dynamics (erosion/deposition) in engineered alpine rivers, and its impact on the morphodynamics of gravel bars. Even if the morphology of these rivers is mainly controlled by bed load transport (and so coarse sediments), fine sediments do affect the dynamics though their interaction with bed load and vegetation through possible deposits on gravel bars. This study will be conducted on the Arc-Isère river system, which is characterized by alternate gravel bar system more or less vegetated and large concentrations of suspended sediment matter (SSM). Following the work of G. Antoine (2013), an important part of the work will be on the SSM dynamics, with a special focus on exchanges between the flow and gravel bars using uni-dimensional modelling. Another objective is to extend local studies on gravel bars (PhDs of M. Jodeau, 2007, M. Jaballah, 2013, and C. Jourdain, 2016) to the whole river system. The study will be both experimental (field measurements, Lidar and aerial picture analysis) and numerical (1D models). An important part of the scientific objectives will be to compare effects of flushing
events carried out by the dam managers and natural floods on the morphodynamics of the river. This PhD work will be partly supported by EDF and the Arc-Isère collaborative study site of the ZABR (Zone Atelier Bassin Rhône), a regional multidisciplinary observatory for the Rhône river basin.