Large-scale morphodynamic modelling of the Gironde estuary, France

Previous attempts at morphodynamic modelling in complex estuarine configuration employ simplifying methods in order to reduce computational cost. Thanks to tremendous progress in numerical and parallelism methods, the open source finite-element Telemac system is applied to represent the medium term bed evolution in the largest estuary in France, the Gironde macro-tidal estuary. A depth-averaged approach is selected here as a good compromise between model accuracy and computational cost. Computations are performed using as bed material either uniform sand or graded sand. Both approaches are compared on measurements of suspended load and bed changes. The suspended rates are better reproduced by the graded sediment assumption and the morphodynamic model results show qualitative agreement with observations of the bed evolution in the central part of the estuary.