Scour at Breakwaters Under Combined Waves and Current

Bed profiles perpendicular to breakwater have been measured for orthogonal combined wave and current scour. The bedprofiles show the distinct features of the wave scour forming due to the presence of recirculating cells, namely deposition/scour at the antinodes/nodes depending on whether the sediment transport occurs in the no-suspension or the suspension mode.

Also, the current scour which forms by the presence of secondary flow as a result of the corner flow and the change in roughness is noticeable in the bed profiles. The mechanism of scour in both the fundamental cases (waves alone and the current alone) is that the sediment is mobilized by the primary flow while the secondaryflow/recirculating cells cause a mean transport of sediment, leading to scour.

For the orthogonal combined wave andcurrent the mechanism appears to be similar.