On the behaviour of tidal current directions due to the presence of submarine sand waves

Processes controlling the dynamics of compound sand waves in the North Sea, Netherlands

“…Near sand wave crests, the angle between crest orientations of sand waves and megaripples is thus 19.6°. This corresponds well to the orientation angles between sand wave crests and megaripple crests reported in the literature [e.g., Terwindt , 1971; Malikides et al , 1989; Lanckneus and De Moor , 1991; Hennings et al , 2000].…”

“…The angle between the crest orientations of sand waves and superimposed megaripples as observed in the offshore area is explained by the deflection of the tidal current over sand waves due to the Bernouilli effect, which is the deflection of the flow direction by current velocity variations over bottom undulations [ Terwindt , 1971; Malikides et al , 1989; Hennings et al , 2000]. The implied deflection of the tidal current is confirmed by the systematic change of megaripple crest orientations over the length of a sand wave, as observed in the offshore area (Figure 6).…”

“…The hypothesis that sand waves are relic forms from former conditions [e.g., Hennings et al , 2000] has been refuted by (1) their sharp‐crested cross‐sectional profiles, (2) the positive relation between upper/lower lee migration, (3) albeit slowly, they migrate (rates > 1 m yr −1 ) and aggrade vertically and are thus contemporarily being developed, and (4) the formation and active development of smaller superimposed bed forms such as the bifucation and straightening of megaripple crests.…”

Morphology and dynamics of large subtidal dunes in Bahia Blanca estuary, Argentina

“…However, in other works (Aliotta, 1987;Aliotta and Perillo, 1987;Waage, 2012) Several investigations (Harris, 1982;Lees, 1983;Twichell, 1983;Collins et al, 1995;Reynaud et al, 1999;Hennings et al, 2000) have shown that the dunes' asymmetry and geometry in cross-section have been widely used as indicators of net bedload sediment transport and hydrodynamic conditions. Following these concepts, the asymmetric shape and orientation of large and small-scale dunes in our study area clearly reveal the ebb flow dominance in the navigation channel.…”

Modelling sand wave variation

“…This can happen due to a changing water depth, but also indirectly by locally changing the tidal current. If we take into account that sand waves can significantly change both the local water depth and, through this, the current velocity (Hennings et al, 2000), surface wave characteristics are expected to change over sand waves. Though the effect of surface waves is incorporated in a few linear studies of sea bed morphodynamics (e.g.…”