Shashank GUPTA (2019-2022)
PhD student in laboratory experiments
Supervisors: Céline Berni (Irstea Lyon) and Benoît Camenen (Irstea Lyon)
Ecole doctorale : MEGA  (Mechanics, Energetics, Civil Enginnering, Acoustics), Lyon

Laboratory experiments on fine sediment erosion and deposition in an alternated bar system and its impact on bar morphodynamics.

Engineered alpine rivers are often characterised by alternated bar systems and substantial sediment transport, particularly of fine sediments (clay, silts and sands). A current problem is the gravel bar aggradation due to successive deposits of fine materials and the growth of riparian vegetation. Such evolution can increase the flood risk in mid and long-term. The purpose of this project is to study in laboratory experiments, the fine sediment dynamics (erosion and deposition) and their impact on bar mobility. This PhD is part of a larger project including also field studies and numerical modelling and will focus on the processes at stake at the bar scale. We will first focus on the effect of porosity on deposition and erosion locations. For this, we will compare experiments on both mobile porous bed (made of gravel) and impermeable fixed bed. Second, we will try to investigate the effect of unsteady flow and more  precisely the shape of a hydrograph, on the deposits. Third, the impact of the extent of the clogging on bar morphodynamics will be quantified.