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

Three-dimensional modelling of salinity and sediment suspension in The Loire estuary: coupling of processes

Sogreah – 6 rue de Lorraine, 38130 Echirolles

Auteur de correspondance : regis.walther@sogreah.fr

Abstract

The Loire estuary management agency, the “Groupement d’Intérêt Public Loire Estuaire”, appointed Sogreah to study, develop and evaluate scenarios aimed at improving the hydrosedimentary functioning of the Loire estuary. This assignment notably includes a three-dimensional hydrosedimentary model of the estuary. This comprehensive model, built using the TELEMAC-3D modelling system developed by EDF-R&D, was compared with two large series of field measurements and with historical data, which has substantially increased the available knowledge of tide dynamics in the estuary. It has been proved that the presence of liquid mud in the inner estuary leads to a remarkable drop in the low-water levels, sometimes exceeding a metre. This means it is essential to couple the friction calculation and the maximum turbidity zone dynamics in order to gain an accurate appraisal of the impact of developments in the estuary. This discovery calls into question the traditional approach consisting in mapping friction as a function of the Loire discharge alone.