Variability of sediment processes around a tidal farm in a theoretical channel

Sediment transport plays a crucial role in coastal ecosystems and is one of the least known parameters in high energy sites. The recent development of tidal energy projects challenges the scientific community to better understand this natural phenomenon and the interactions with tidal turbines. Using MIKE21/3 software from DHI, a benchmark for sediment transport model was developed with simulations with and without a tidal farm in idealised two and three-dimensional tidal channels. Results reveal that a 2D approach is sufficient for regional scale morphological assessments, however 3D models allow for a closer examination of influences around the tidal farm. Differences in calculating sediment transport rates based on approaches after Engelund & Fredsøe and Van Rijn formulae illustrate the degree of uncertainty in modelling sediment transport rates. Results for the Engelund & Fredsøe models also show that they are sensitive to mesh resolution in equilibrium conditions and are more stable in non-equilibrium conditions for the bed level change rates. Tests have also demonstrated that models using Engelund & Fredsøe formulae are more sensitive to physical characteristics than models based on Van Rijn, accentuating the necessity to evaluate sediment transport formulae with field data before making a choice of model.