A large scale morphodynamic process-based model of the Gironde estuary

Abstract

We present here our effort to develop a morphodynamic model of the Gironde estuary, using a process-based approach. In this complex and strongly dynamical environment, internal coupling between the flow (Telemac-2d) and sediment transport models (Sisyphe) allows the representation of detailed sediment processes and interactions with the bed, using a bed roughness feedback method. In this complex and highly heterogeneous environment, the sediment bed composition had to be schematized assuming 3 classes of bed material. Model results could be further improved by accounting for the cohesive sediment (consolidation processes). Thanks to parallelization of the codes, the simulation takes only 18 hrs on 8 processors (linux station) to calculate the 5-year bed evolution, at the basin scale (150 km).

A case study of sediment transport in the Paranagua Estuary Complex in Brazil

“…Sediment transport and morphological changes in estuaries have recently attracted great deal of attention due to environmental concerns and problems associated with siltation in harbours and navigation channels (Cronin et al, 2009;Giurdino et al, 2009;Villaret et al, 2012). Numerical modelling based on processbased approach has been widely applied to estimate sediment transport by fluid flow which is driven by forces arising from tides, waves, wind and salinity.…”

Two-dimensional modeling of fine sediment transport with mixed sediment and consolidation: Application to the Gironde Estuary, France

“…where u* is the shear velocity, m/s. Consolidation processes are accounted for with an iso-concentration multi-layer consolidation model for mixed sediment (Villaret et al, 2011;Villaret & Walther, 2008) that assumes that the vertical flux of sediment between layers is proportional to the sediment mass in each layer, via the use of mass transfer coefficients. This approach was chosen to consider the sediment as a mixture in bed consolidation and differs from previous studies which include bed consolidation using the Gibson theory (Santoro et al, 2017;Thiebot et al, 2011;Van, 2012) with mud only.…”

“…The second group analyzes the turbidity maximum dynamics via threedimensional models with a fixed bed configuration (Cancino & Neves, 1999;Diaz et al, 2018;Li et al, 1994;Sottolichio et al, 2001;van Maanen & Sottolichio, 2018). The last group focuses on two-dimensional, depth-averaged models (2DH) of sediment transport and bed evolution (Chini and Villaret, 2007;Huybrechts & Villaret, 2013;Van, 2012;Villaret et al, 2011). Huybrechts and Villaret (2013) simulated a 5 year morphodynamic evolution using three sand classes, while Villaret et al (2011) and Van (2012) did numerical simulations considering cohesive sediment and bed consolidation.…”

“…The last group focuses on two-dimensional, depth-averaged models (2DH) of sediment transport and bed evolution (Chini and Villaret, 2007;Huybrechts & Villaret, 2013;Van, 2012;Villaret et al, 2011). Huybrechts and Villaret (2013) simulated a 5 year morphodynamic evolution using three sand classes, while Villaret et al (2011) and Van (2012) did numerical simulations considering cohesive sediment and bed consolidation.…”