Abstract
Banks Strait, Tasmania, Australia, has been identified as a potential site for the deployment of tidal turbines. In this study, the characterization of sediment transport and large sand waves for this site is performed. Observations of bed level change collected from surveys in 2018 showed a migration of large sand waves over a period of nine months. Migration rates in an excess of one hundred meters for nine months were found, which are large compared to the rate reported at other coastal sites, by several meters per year. A validated hydrodynamic model is coupled with a morphodynamic model to perform sensitivity tests and identify what parameters influence migration to better understand sediment dynamic in the Banks Strait. Numerical analysis showed a constant shift of the sand waves profile in an eastward direction, consistent with the observations. This migration was strongly linked with tidal asymmetry, with a residual current flowing towards the east. The principal parameters driving the migration of sand waves in the Banks Strait were found to be sediment sorting, bed friction and residual current. This study gives new insights for the seabed of Banks Strait and provides an assessment of the natural variability of sediment for futures tidal farms deployments.
Highlights
Increasing activity in ocean renewables and blue economy is driving the need to understand natural sediment processes and their variability and to understand the potential influence of anthropogenic activities on them
More complex numerical shallow models were used to investigate the formation, migration and the effect of parameters on the evolution of sand waves: Tonnon [5] with the study of artificial sand waves, Borsje [37] who studied two turbulence models associated with bed load transport only, Van Gerwen [38] who focussed on formation of sand waves with comparable migration patterns to observations, and Wang [39] who examined the sensitivity of sand waves to environmental factors
The model was developed to evaluate the sediment dynamics in the Banks Strait and the reference case revealed a high value of the mean bed shear stress, the principal parameter driving sediment transport (Figure 10)
Summary
Increasing activity in ocean renewables and blue economy is driving the need to understand natural sediment processes and their variability and to understand the potential influence of anthropogenic activities on them. More complex numerical shallow models were used to investigate the formation, migration and the effect of parameters (tidal forcing, significant wave height, turbulence scheme, sediment size) on the evolution of sand waves: Tonnon [5] with the study of artificial sand waves, Borsje [37] who studied two turbulence models associated with bed load transport only, Van Gerwen [38] who focussed on formation of sand waves with comparable migration patterns to observations, and Wang [39] who examined the sensitivity of sand waves to environmental factors. In the Banks Strait, significant wave–tide interactions were found by [42,43]; it is crucial to consider wave forcing for the sand transport in this tidal energetic site.
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