Numerical modelling of seabed disturbance and sediment mobility, with applications to morphodynamics on the storm-dominated Sable Island Bank, Scotian Shelf

Michael Z. Li, Qingping Zou, Charles Hannah, Will Perrie, Robert Prescott, Bechara Toulany

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Abstract

Waves, tidal currents, wind-driven and circulation currents, and sediment mobility were modelled for one full year over the storm-dominated Sable Island Bank (SIB), Scotian Shelf. The mean shear velocity of tidal current and that of the wind-driven and circulation current are less than 2 cm/s, but the peak mean wave and combined wave-current shear velocities reach 4 and 4.5 cm/s respectively. Comparison between the model-predicted shear velocity and bedload threshold suggests that the circulation and wind-driven currents cause minimum sediment mobility on SIB. Tidal current and waves can each cause sediment mobility at least once a year over 36% and 71% of the bank area respectively, while the combined wave-current shear can cause sediment mobility over 93% of the bank area. Calculated time percentages of sediment mobility caused by various processes indicate that wave or wave-dominant disturbance is most important and occurs over >50% of the bank area, while mixed disturbance is also significant and occurs over ~ 30% of the bank area. Tide or tide-dominant disturbance occurs over only 10% of the bank area. Several parameters are proposed as universal indices for quantifying seabed disturbance and sediment mobility for coastal and shelf environments.This distribution and mobility of various mid-sized bedforms were correlated with the seabed disturbance parameters. Updated bedform distribution was compared with seabed disturbances predictions to define seven bedform zones on SIB.
Original languageEnglish
TypeGeological Survey of Canada, Open File 6155
Media of outputpaper; on-line; digital
PublisherGeological Survey of Canada. Open File 6155
Number of pages1
DOIs
Publication statusPublished - 8 Sep 2009

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