Sediment Transport on Roberts Bank: A Sandy Intertidal Flat on the Fraser River Delta

Abstract

Abstract Waves and currents were monitored over a range of incident forcing between March 23 and April 24, 2003, on Roberts Bank, the sandy intertidal portion of the Fraser River Delta. A comparison of the dimensionless, current-induced skin friction with the critical skin friction for the initiation of sediment motion suggests that the currents are only capable of entraining sediment briefly with the ebbing tide or when enhanced by the wind. Since these wind-generated currents are associated with storm waves, which typically exceed the critical skin friction, they have a disproportionately large impact on the direction of the sediment transport. An energetics-based model, driven by locally measured near-bottom currents, is used to characterize the rate and direction of bedload and suspended load transport. The largest transport rates were predicted in response to storm waves and were initially directed onshore with weak oscillatory transport and alongshore by wind-generated currents that turned offshore ...