Tidal-stream Energy Converter (TEC) arrays are expected to reduce tidal current speeds locally, thus impacting sedimentary processes, even when devices are positioned above bedrock. Tidal dissipation can produce high suspended sediment concentrations (turbidity maxima) which are important for biological productivity. Also, devices will potentially impact morphological features further afield, e.g., offshore sand banks and beaches. Yet few impact assessment studies of potential TEC sites have looked closely at sediment dynamics beyond local scouring issues. It is therefore important to understand to what extent exploitation of the tidal energy resource will affect sedimentary processes, and the aim of this research is to assess the scale of this impact in relation to natural variability, caused by both tidal currents and wave-induced currents.