Surf Zone Circulation and Transient Rip Currents on a Microtidal and Wave Dominated Open Coast Beach, Gold Coast, Australia

Abstract

Surf zone circulation patterns are recognised in the literature as having an important influence on cross- and alongshore exchange of water, sediment, and floatsam in the surf zone. Any study of surf zone circulation patterns therefore has implications for sediment transport, biological processes and beach safety, with the majority of studies focusing upon rip current circulation and rates of cross-shore exchange of drifters due to rip currents. The aim of recent research has been to describe surf zone circulation patterns and retention of floatsam in the surf zone, with a major focus on informing rip current escape strategies and hazard mitigation. Previous studies have focused upon single bar embayed beaches in a microtidal environment or open coast beaches in a mesotidal or macrotidal environment, exposed to a generally shore-normal wave climate and displaying relatively stable bar morphology. This thesis explored surf zone circulation patterns and transient rip currents on the open beaches of the northern Gold Coast, Australia. These beaches are characterised as being microtidal and wave dominated, double bar, open coast beaches with no bounding headland morphology. The beaches are exposed to a highly variable wave climate, which is often bimodal and bidirectional and the dominant angle of wave approach is oblique to the shoreline. The double bar beach state combinations are complex and highly dynamic and sandbar and rip features are often skewed in response to the oblique angle of wave approach and prevailing longshore current.