Résumé
River mouths along sandy coastlines are influenced by alongshore transport of littoral sands and the interaction of hydrodynamics processes at the river mouth. These interaction are responsible for opening/closure of river outlets and subsequent episodes of sand bypassing by spitbreaching. Here, we study these mechanisms of alongshore sediment bypassing at a river mouth along the French Mediterranean coast. Over the last 6 years, bypassing processes were found to be associated with spit elongation and spit breaching. Hydrodynamics measurements were implemented in order to assess the respective role of river jet and wave conditions on these opening/breaching episodes. Results tends to point on one major mechanism: spit overtoping that induces breaching. For the floods events analysed, the river jet has apparently only a very low contribution to this opening.