Methods for medium-term prediction of the net sediment transport by waves and currents in complex coastal regions

Medium-term prediction of sediment transport and morphological behaviour in the coastal zone is becoming increasingly important as a result of human interference and changing environmental conditions. The interaction of waves and tides is shown to play a pivotal role in the net (annual) sediment transport and morphodynamics of the coastal zone. The Telemac Modelling System has been applied to the Dyfi Estuary and neighbouring coastline, mid Wales, to recreate the annual wave–current conditions and the resulting sediment fluxes. ‘Input reduction’ methods have been required to produce realistic schematisations of events in practical computation times. A field campaign carried out in 2006 provided data for validation of the flow module (Telemac-2D) and also observations to verify the patterns predicted by the wave module (Tomawac). To improve model accuracy refinements were implemented with regard to the sand transport formulation used in the sand transport module (Sisyphe). Here, a parameterisation of the results from the UWB 1DV sand transport ‘research’ model, for the conditions in the Dyfi Estuary, has been introduced, allowing Sisyphe to provide greater realism in the morphological predictions. The model predictions are presented along with a discussion of the success/failure and limitations of the modelling methods applied.