Wind-wave and Tidally Driven Sediment Resuspension in a Macrotidal Basin
A coupled hydrodynamic-wave-sediment model is used to simulate the broad-scale tidal circulation, surface waves, and suspended sediment concentrations (SSC) in Minas Basin, a 70-km long tidal estuary in the Bay of Fundy, during winter and summer periods. The model hydrodynamics are validated using acoustic-Doppler current profile observations, the surface SSC predictions are compared to satellite observations, and model results indicate that strong seasonal signals in SSC can be explained in part by seasonal changes in fetch-limited surface waves generated by local winds over the basin. The spatial and temporal variability of SSC is evaluated in this study by focussing on different forcing conditions from waves and tidal currents, the two primary physical process that influence the response of sediments in suspension. Model predictions in the intertidal areas indicate that surface waves can increase the bed shear stress from tidal currents alone by up to 1–5 Nm− 2, causing excess bed shear stresses to be higher and result in higher SSC by 100–200 gm− 3 particularly during wind events that are stronger and more frequent in winter months. Resuspension of sediments on tidal flats is driven by the combination of shear stresses from near-bed wave orbital velocities and tidal currents, and transport of the suspended materials over deeper areas of the basin is driven by advection from the strong tidal currents.
KeywordsCoastal oceanography Tidal currents Wind-generated surface waves Suspended sediments Numerical modeling Field observations Satellite observations
The authors thank Danika van Proosdij (Saint Mary’s University) for the OBS data and discussions on sediments in tidal marshes; Gordana Lazin and Gary Bugden (Bedford Institute of Oceanography) for processing the satellite data and the ADCP observations; and Tim Milligan and Brent Law (Bedford Institute of Oceanography) for discussions on sediment dynamics in the Bay of Fundy. Detailed comments from two anonymous reviewers are greatly appreciated. This research was supported by the Offshore Energy Research Association of Nova Scotia (OERA) and by the Natural Science and Engineering Research Council of Canada (NSERC) Discovery Grant program of the first author.
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