Modélisation tridimensionnelle de la salinité et de la turbidité dans l’estuaire de la Loire : couplage des processus

Walther, Régis; Bertrand, Olivier; Rieu, Jérôme; Hamm, Luc

doi:10.1051/lhb:2007046

Cited by 2 publications

(1 citation statement)

References 6 publications

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“…This issue was particularly important in the Rochefort area, because of fluid mud in the channel, which can cause a significant increase in current velocities, the physical roughness of the sediment bed being very low. Walther (2009) andWalther et al (2007) showed that hydrodynamic models often fail to reproduce this effect and overestimate low water levels. King and Wolanski (1996) made similar observations.…”

Section: Model Validationmentioning

confidence: 99%

Formation and structure of the turbidity maximum in the macrotidal Charente estuary (France): Influence of fluvial and tidal forcing

Toublanc

Brenon

Coulombier

2016

Estuarine, Coastal and Shelf Science

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a b s t r a c tUnderstanding estuarine sediment dynamics and particularly turbidity maximum dynamics is crucial for the management of these coastal systems. Various processes impact the formation, movement and structure of the turbidity maximum. Several studies have shown that tidal asymmetry and density gradients are responsible for the presence of this suspended sedimentary mass.The Charente estuary is a highly turbid system (with suspended sediment concentrations often in excess of 5 g/L) that remains poorly understood despite its strong impact on local activities. In this study, a three-dimensional hydrosedimentary model is developed to represent the sediment dynamics of this estuary. Model validation demonstrates good accuracy, especially on reproducing semi-diurnal and spring-neap variability. Several simulations are performed to evaluate the influence of tides and river discharge on the turbidity maximum. Mean and maximum suspended sediment concentrations (SSC) and sediment stratification are calculated. SSC transects are also used to visualize the suspended sediment distribution along the estuary.The turbidity maximum generally oscillates between the river mouth and the Rochefort area (20 e30 km upstream). The model shows strong variations at different time scales, and demonstrates that SSC is mainly driven by deposition/resuspension processes. Spring-neap comparisons show that the turbidity maximum is not well-defined during neap tides for low and mean runoff conditions. Simulations of spring tides and/or high runoff conditions all result in a compact suspended sedimentary mass.Performing simulations without taking density gradients into account demonstrates that tidal asymmetry is the main mechanism leading to the formation of the turbidity maximum. However, density gradients contribute to maintaining the stability of the turbidity maximum. Vertical stratification traps sediments at the bottom. Longitudinal stratification ensures a sharper edge at the downstream limit of the suspended sedimentary mass, preventing a massive export of sediments.

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Section: Model Validationmentioning

confidence: 99%