Three-Dimensional Sediment Transport Modeling of the Gironde Estuary

Abstract

A 3D model of the Gironde estuary has been built to predict the flow pattern, sediment transport and associated bed evolution. The bed friction is estimated using the bed roughness predictor of van Rijn. It requires to provide a distribution of the sediment at the bottom as the percentage of mud content influences the bed friction and associated sediment transport. Due to limited data availability, some assumptions about the bed mixture are necessary to feed the numerical model. The accuracy of the methodology has been assessed through comparisons with in situ data (water level, velocity and salinity). Accuracy is water levels is about 15 cm and the relative errors are lower than 20% for velocity and salinity for most of the stations. The numerical model has then been used to highlight the sensitivity of the bed distribution: initial bed composition, bed load and fluid mud attenuation. Finally, the evolutions of flow and bed patterns have been analyzed for two contrasted hydrological conditions.