Author(s): Zsolt Vecsernyes; Amandine Jaeger; Ulysse Beytrison; Toufik Bekaddour; Nicolas Andreini

Linked Author(s): Zsolt Vecsernyes

Keywords: Keywords: Hybrid modelling; Movable-bed physical model; Flow-3D numerical simulation; Suspended and bed load simulation; Fish pass

Abstract: Due to its alpine nival regime, the Arve River (F-CH) has a particularly heavy sediment transport causing frequent clogging of the Vessy right-bank fish pass. The Service industriel de Genève inquired a detailed analysis from the Laboratory for Applied Hydraulics of HEPIA Geneva-CH to develop a sustainable solution replacing the inoperative right-bank fish ladder by a bypass river. A hybrid modelling carried out on a movable-bed physical model and by 3D numerical simulation yielded a robust solution protecting the new bypass river from clogging. Arve’s bed-load is hence not transferred by the water intake to the bypass river, which is also protected from fin sediment deposit. The movable-bed physical modelling (scale 1:40) yielded a solution preserving the bypass river from Arve’s bed-load (Vecsernyés et al. 2019). The developed double-groin structure implemented in front of the water intake deviates the bed load. The plunging flow observed between the groins engenders a scouring mechanism, which guarantees a clear waterway for fishes between the new fish pass and the Arve River, revealed also by KMnO4 dye tracer. This fish path persists even during low-flow conditions consecutive of high-turbidity floods. The dye tracer also highlighted varying conditions of turbulence behind the water intake and within its hydraulic works. All hydraulic works of the water intake as well as Arve’s local morphology were numerically modelled on Flow-3D. Consecutive flood/low-flow conditions were tested by parallel numerical and physical simulations. The 3D numerical simulations helped to refine the double-groin arrangement and to reduce fine sediment deposit potential in front of the water intake. They yielded relevant results and an appropriate choice of the hydraulic structure behind the water intake too, preventing the new fish pass from clogging by fine sediment. Since the hybrid modelling provided a robust solution in complex hydrodynamic and sediment transport conditions the new bypass river and its hydraulic structures can be implemented in the Vessy meander of the Arve River.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022624

Year: 2022