Large-scale exploitation of the tidal stream resource is likely to alter the regional hydrodynamics, but for practical extraction scenarios this effect is generally considered to be very small. However, since sediment transport is proportional to the cube of velocity, relatively small changes in the tidal currents could translate into large changes in the sediment dynamics. Here, we investigate this effect in relation to two oceanographic processes: tidal asymmetry and headland sand bank maintenance. Both of these processes have major practical significance. Tidal symmetry/asymmetry is responsible for the large-scale long-term distribution of shelf sea sediment. Any tidal energy scheme which has the potential to alter this large-scale distribution could affect the supply of sediment feeding into natural coastal defense systems which remove energy from storm waves, such as beaches and offshore sand banks. Headlands are some of the most attractive regions for exploitation of the tidal stream resource. Any tidal energy scheme which could lead to changes in the morphodynamics of the associated headland sand banks could have implications for coastal flooding, due to changes in the wave distribution, including wave refraction and depth-induced wave breaking.