COUPLED 3D MODELING OF TURBIDITY MAXIMUM DYNAMICS IN THE LOIRE ESTUARY, FRANCE

Regis Walther, Julien Schaguene, Luc Hamm, Eric David

Abstract


Comprehensive 3D modeling efforts to understand salt intrusion and fine sediment dynamics in the Loire estuary started in 2006 and first results about the role of fluid mud on the hydrodynamic circulation through the bottom roughness was reported by Hamm and Walther during ICCE 2008. Recent progress since 2008 includes a) the coupling between the three modules (hydrodynamic, salinity, fine sediment transport) in order to let the fluid mud control the bottom roughness, b) the improvement of the vertical turbulence model enabling to reproduce strong stratifications observed during neap tides, c) a new empirical consolidation model calibrated against lab measurements and including the quantification of the erosion rate over a large range of bed dry densities and d) a new parameterization of the settling velocity function of the turbulence level of the flow. These developments have been validated over a period of five months in winter against field measurements of salinity and turbidity acquired through a permanent network of fixed sub-surface turbidimeters established in 2007. Additional validation against bathymetric measurements of the position of the fluid mud layer in the navigation channel is also presented.

Keywords


estuary; maximum turbidity; salinity; vertical turbulence; 3D modeling; TELEMAC system

References


Hamm L. and Walther R., 2008. Morphodynamic coupling of bottom roughness and fluid mud for modeling tidal propagation in the Loire estuary (France). Proc. 31st Int. conf. on Coastal Engng;, Hamburg, World Scientific, 2832-2841

Sanchez M., Grimigni P. et Delanoe Y., 2004. Distribution des sédiments cohésifs en relation avec la vitesse de la phase solide dans l'estuaire de la Loire . Comptes-rendus des VIIIemes journées Nationales Génie Civil-Génie Côtier, Compiègne 7 et 9 septembre 2004.

Sanchez M., Levacher D., 2008. Erosion d'une vase de l'estuaire de la Loire sous l'action du courant. Bull Eng Envir, 67, p597-605http://dx.doi.org/10.1007/s10064-008-0159-9

Viollet P.L., 1980. Turbulent mixing in a two-layer stratified shear flow. Second Int. symp. On stratified flows. The Norwegian Institute of technology, Trondheim, Norway, 24-27 June 1980


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