Morphodynamics modelling and optimization of forcing self bed-scour by groynes in a meandering reach.

Pablo Tassi, Kamal El kadi Abderrezzak, Dongchen Wang, Nicolas Claude

Tuesday 30 june 2015

12:33 - 12:36h at Oceania (level 0)

Themes: (T) Sediment management and morphodynamics, (ST) River morphodynamics, Poster pitches

Parallel session: Poster pitches: 5B. Sediment - River

River training works and protection against erosion refer to a large variety of engineering measures and practices that support, among others, navigability, aquatic habitat and safety against flood risk. Sediment dredging emerges as an essential operation that commonly needs to be considered in a river training plan, such as maintaining a minimum water level at the entrance of a water intake for a pre-determined width. Nevertheless, in some situations dredging is a costly operation that needs to be repeated periodically, sometimes with unpredictable or even unwelcome consequences. To mitigate these shortcomings, it can be desirable to propose different solutions adapted to the situation under interest. Alternatives to dredging include groynes or wing dikes. These structures are designed to ensure that the river retains a sufficient depth without continual dredging, and prevents the formation of sand bars. The objective of this work is to develop 2DH morphodynamics numerical models to investigate the influence of engineering solutions (groynes) by forcing self bed-scour and optimizing their location. The study pilot site is a 25km low-land sand-gravel bed meandering reach of the Loire river, located upstream of the Orleans city in north-central France. Preliminary numerical simulations performed with the open-source Telemac-Mascaret Modelling system showed that the hydrodynamics module (Telemac-2D) coupled with the sediment transport and bed evolution module (Sisyphe) reproduce qualitatively well the main characteristics of the morphodynamics structures observed in the study zone. The analysis of different configurations and scenarios showed that the model could be applied to practical engineering works.