Comparison of sedimentary flux: measured in-situ versus simulated

This paper discusses the abilities of numerical models to predict the morphodynamics over sandy beds. In the first part the sediment transport model is presented which solves the bed evolution equation in conjunction with sediment transport formulas. The flow field and the water depth are calculated using the depth-averaged hydrodynamic model TELEMAC-2D. The work consisted in setting up the methodology of calculation [3]. The principle is to make an external coupling of three codes where Artemis models swell propagation; Telemac2D calculates the currents and Sisyphe determined the morpho-dynamic evolution [5]. The basic principle of this external coupling is to make this loop on the codes with a step of morpho-dynamic time depending essentially on weather conditions and on the hydrodynamic forcing of the studied beach. These models were used in the framework of a simulated meteorological cycle describing the seasonal evolution of hydrodynamic factors. Figure 1 Localisation of the "plage de la Corniche" at Sète in Mediterranean Sea Figure 2 Location of study sites for the sediment fluxes measurements The objectives through this study are multiple. First, we are going to set up a procedure of linking of three codes to be able to simulate realistic climates. This technique of simulation will then use to compare and studied the contribution of the various formulae of sedimentary transport (as in [1] on the site of Sète during two specific storm [4], see figure 1). Figure 3 In -situ data Qsm (Hardelot) and simulated Qsc (first approach, with Bijker) longshore sediment fluxes (depth average around 1m). Figure 4 In-situ data Qsm (Wissant) and simulated Qsc (first approach, with Van Rijn) longshore sediment fluxes (depth average around 1m) We improve this methodology to simulate the Rising-Apex-Waning of a Storm event. We also present a comparison of the velocity at these different periods of the storm. To calibrate all theses sediment formulae, we also compare our simulations with in-situ data of sediment transport measured on several beaches of the North sea and of The English Channel [2] see figure 2, 3 and 4. AcknowledgementsThis work has been supported by French program RELIEF MICROLIT and French Research NationalAgency (ANR) through the Vulnerability Milieu and Climate program (project VULSACO, n° ANR-06-VMC-009) References[1] Camenen, B. and Larroudé, Ph., 2003, Comparison of sediment transport formulae for a coastalenvironment, Journal of Coastal Engineering, 48, pp. 111-132.[2] Cartier, A. and Héquette, A. – 2011 – Estimation of longshore and cross-shore sediment transporton sandy macrotidal beaches of northern France. Proceedings Coastal sediment 11’, 7 InternationalSymposium of Coastal Engineering, Miami, Etats-Unis, 2-6 mai 2011, pp 2130 2143. [3] De Vriend, H.J. and Stive M.J.F., 1987. Quasi-3D Modelling of Nearshore Currents. CoastalEngineering,11: 565-601. [4] Gervais M., Balouin Y., Belon R., Certain R., Robin N., Berne S., Impacts des tempêtes sur lamorphologie d'un littoral microtidal : le site du Lido de Sète à Marseillan, Golfe du Lion.DOI:10.5150/jngcgc.2010.032-G, pp. 263-274. [5] Hervouet, J.M., Hydrodynamics of Free Surface Flows: Modelling With the Finite ElementMethod, 2007, John Wiley and Sons, 360p. [6] Larroudé Ph., 2008, Methodology of seasonal morphological modelisation for nourishmentstrategies on a Mediterranean beach. Marine Pollution Bulletin 57, pp 45-52.