Articles | Volume 2, issue 2
Earth Surf. Dynam., 2, 443–453, 2014

Special issue: Frontiers in river, coastal and estuarine morphodynamics

Earth Surf. Dynam., 2, 443–453, 2014

Research article 21 Aug 2014

Research article | 21 Aug 2014

Sediment dynamics on a steep, megatidal, mixed sand–gravel–cobble beach

A. E. Hay1, L. Zedel2, and N. Stark1,* A. E. Hay et al.
  • 1Dalhousie University, Department of Oceanography, Halifax, Canada
  • 2Memorial University of Newfoundland, Department of Physics and Physical Oceanography, St. John's, Canada
  • *now at: Virginia Tech, Department of Civil and Environmental Engineering, Blacksburg VA, USA

Abstract. Results are presented from a pilot study of shore-face sediment dynamics on a steep, poorly sorted, coarse-grained, megatidal beach at the head of the Bay of Fundy, Nova Scotia, Canada. The experiment involved the first field deployment of a prototype wideband, pulse-coherent, bistatic acoustic Doppler profiling system. Measurements of the vertical structure of flow and turbulence above a sloping bed, as well as bed material velocity, demonstrate the capabilities of this instrument vis-à-vis studies of nearshore sediment dynamics at the field scale. The second focus of the paper is the unexpected observation that the surficial sediment median diameter, across the lower two-thirds of the intertidal zone, underwent a pronounced decrease when wave forcing was more energetic, compared to values observed during calmer conditions. The explanation for this result appears to involve the formation – in wave-dominated conditions – of metre-scale wavelength, 20 cm high ripples on the rising tide, which are then planed flat by the swash and/or the shore break on the subsequent ebb.