Influence of seabed slope and Coriolis effects on the development of sandbanks near headlands

The mechanism responsible for asymmetric sediment accretion around an idealized, symmetrical headland is clearly the Coriolis force. What is not evident, however, is how the Coriolis force manifests itself in the headland dynamics to promote asymmetric depositional patterns. In this study, patterns of scour and accretion, topographic and advective vorticity, bed load, and suspended load transport pathways around a theoretical coastal headland are examined. Previous studies have emphasized the contribution of the Coriolis force to a secondary flow mechanism, "tidal stirring." This investigation provides evidence to suggest that secondary flow dynamics are not significant in sandbank generation associated with headlands. It further demonstrates the direct contribution of the Coriolis force in reinforcing inertial terms, near-headland scour, and asymmetric accretion. Examination of the vorticity balance throughout the simulations reveals that high levels of slope-induced topographic vorticity act in direct opposition to advective vorticity near a headland tip. It is also demonstrated that the Coriolis force manifests itself in the production of vorticity. This has been used in the investigation as a means of detecting the sensitivity of the flow to the Coriolis force. In regimes where advective and topographic vorticity production is very similar ( flat bed cases), it is found that bed evolution is more sensitive to the Coriolis force. In regimes where topographic vorticity clearly dominates the vorticity balance ( in seabed slope case), the influence of the Coriolis force becomes less important.