Modelling sand/mud transport and morphodynamics in the Seine river mouth (France): an attempt using a process-based approach

Abstract

The mouth of the Seine River estuary (France) has undergone marked morphological evolution over several decades mainly due to engineering works aimed at improving access to Rouen and Le Havre harbours. The intertidal areas are decreasing in size and the lower estuary is accumulating sediment and prograding. In order to understand and better describe the major morphological behaviours of the estuary, a morphodynamic numerical model was developed within the Seine-Aval program. At the end of the 1st part of the research program, a validated fine sediment transport model (3D) was available (Le Hir et al., 2001b). As the present morphological study addresses medium-term issues (a few decades), and because of the need to investigate impacts of local structures or events, we chose to use the so-called ''process-based approach'' starting from the existing model. First, the existing model was upgraded to account for (suspended) sand transport, and to achieve coupling between morphological changes and sediment transport. Erodability of the sediment accounts for the respective proportions of mud and sand. Simulations starting from an arbitrary surficial sediment cover show that the model is able to reproduce realistic sediment patterns. For example, it is able to change the sediment nature on the intertidal flat near Le Havre from sand to mud. Observed structures of suspended sediment are also reproduced: fine particles mainly follow the turbidity maximum whereas significant concentrations of sand grains in suspension are found where the hydrodynamic stresses are intense. Concerning morphodynamics, simulations with real forcing over one year are discussed. The effect of waves on the bathymetric evolution of the mouth is shown and the sensitivity of morphodynamics to the coupling procedure is tested.

Hydrodynamic controls of morpho-sedimentary evolution in a rock-bounded wave dominated estuary. Tina Menor (N Spain)

“…Other difference is the absence of a clear ebb-tidal delta as a result of the progradation of the lower estuary. This is the case of other wave-dominated systems like the Senne estuary (Lesourd et al, 2001;Waeles et al, 2007). In our case, only a narrow frontal ebb-lobe is developed showing the dominance of the waves in this sectorThe dynamics in the Bay are characterised by the presence of various sandy flood-tidal deltas and spill-over lobes with varying geometries.…”

Effects of mud supply on large-scale estuary morphology and development over centuries to millennia

“…Mitchener and Torfs, 1996). Over the past decade, mixed sediments have been implemented in several modelling software packages (Van Ledden et al, 2004a;Waeles et al, 2007;Van Kessel et al, 2011;Le Hir et al, 2011;Dam et al, 2016). Long-term morphologic calculations are rare due to computer limitations and lack of spatially and temporally dense data of mud in the bed.…”

Modelling and Analysis of Fine Sediment Transport in Wave-Current Bottom Boundary Layer

“…More expressions could also be found in Ariathurai and Arulanandan (1978), Ariathurai and Krone (1976), Lumborg and Windelin (2003), Parchure and Mehta (1985), Waeles et al (2007) and Wang and Pinardi (2002).…”

“…The first one is to establish shear stress with erosion and deposition flux (Ariathurai and Arulanandan, 1978;Ariathurai and Krone, 1976;Lumborg and Windelin, 2003;Parchure and Mehta, 1985;Waeles et al, 2007;Wang and Pinardi, 2002). The second one is the method of comparison between the reference concentration and the actual concentration (Dou et al, 1995;Galappatti and Vreugdenhil, 1985;Liu, 2009;van Rijn, 1987).…”