The Role of Wave Erosion on Sloping and Horizontal Shore Platforms in Macro- and Mesotidal Environments

Abstract

Abstract Waves were measured over tidal cycles on a sloping, basaltic shore platform at Scots Bay in the macrotidal Bay of Fundy (large tidal range 13.5 m), and on a horizontal, argillite platform at Mont Louis in Gaspe, Quebec (large tidal range 3 m). Video cameras were used to record the height and period of the waves against a series of graduated metal poles anchored along surveyed, shore-normal profiles. Field measurement and theoretical considerations suggest that wave height increases with elevation at Scots Bay, reflecting the occurrence of a gently sloping tidal flat below the midtidal level and higher gradients on the upper than on the lower parts of the platform. Calculated pressures generated within the rock along joints and other discontinuities suggest that wave conditions are suitable for mechanical-wave erosion at Scots Bay. Waves generally break on the low tide cliff at the seaward edge of the platform at Mont Louis, preventing any wave action on the shallow, flooded platform surface behin...