MODELLING OF SEDIMENT TRANSPORT IN A TIDE-DOMINATED COAST. CASE STUDY: CENTRAL DITHMARSCHEN BIGHT, GERMAN WADDEN SEA

摘要

Results of the calibration and validation of a sediment transport model using field measurement data are presented in this paper. The hydrodynamics in the area are mainly driven by tidal action. Cross-sectional field measurement is used to describe the pattern of sediment transport over several tidal conditions, as well as to calibrate and validate the Delft3D two-dimensional numerical model. Predictions of sediment transport under various tidal ranges are performed. Both equilibrium and non-equilibrium formulations were considered. The algebraic formulations for describing bed load sediment transport and bed reference concentration proposed by Bijker and van Rijn were used. The sediment transport model was found to be able to reproduce the principal patterns of sediment concentration and transport dynamics in the investigation area. The use of non-equilibrium formulations in conjunction with the algebraic equation proposed by Bijker improves the agreement with observation. For the conditions in question the predictive ability of the model is in the order of 2. The bed roughness is the key element in estimation of sediment transport concentration. Measurements an empirical equations for estimation of bed forms and roughness showed a clear spatial variation in the tidal channels. The spatial variation of equivalent roughness sizes over the whole region should be taken into account for a more realistic estimation of sediment transport.