To investigate the generation and evolution of IWs as well as their contribution to vertical mixing, a variety of hydro-acoustic devices was deployed in combination with a vertical sampling of suspended particular matter. Wave parameters such as significant wave height, wave frequency, wave length and steepness were computed from these data.
The hydro-acoustic data reveal the formation of a prominent lutocline during slack water, at which IWs begin to be generated with the onset of tidal forcing. The two water bodies, which are characterised by markedly different suspended sediment concentrations, show clear differences in flow behaviour. As a consequence of current shear along the lutocline, Kelvin-Helmholtz instabilities are generated, which then produce IWs.
The IWs break when high shear stresses between the two layers are coupled with great wave steepness, and the breaking causes vertical mixing of the sediment. Most IW breaking events occur during the decelerating ebb phase and thereby promote downstream sediment transport.