Morphology of a Low-Energy Beach, Como Beach, Western Australia

Abstract

The morphology of Como Beach in the Swan River Estuary, Western Australia, is described. Como Beach is in a microtidal estuarine environment in which modal wave conditions are extremely low and nontidal fluctuations in water level are principally determined by storm surges and low-frequency changes in ocean water levels. Detailed descriptions of sandy beaches in very sheltered locations, such as Como, are uncommon in the literature, although these beaches are a common feature of coastal environments. In contrast to beaches in wave-dominated environments, those in very sheltered, low-energy locations may support subtidal terraces and beach profiles that differ in form and scale from the bars and intertidal flats in wave- and tide-dominated environments. At Como, beach profiles are superimposed on a subtidal terrace rising steeply from waters several metres deep to −1.5 m (Australian Height Datum; AHD), then with a low gradient to approximately −0.3 m (AHD) at the shore. The profiles range from planar forms on which very small waves (Hb less than 0.1 m) are dissipated to curvilinear forms that reflect higher waves (Hb > 0.2 m) from the beachface. A transitional form with a segmented profile comprising a steep beachface and flat inshore occurs, particularly where littoral drift is apparent.