PROFILE SEQUENCE AND SEDIMENT DISTRIBUTION OF AN EMBAYED BEACH: FRESHWATER BEACH, QUEENSLAND, AUSTRALIA

Embayed beaches are abundant throughout the coastlines of the world. Typically, these asymmetric beaches are characterized by a curved shadow zone, a gently curved middle transitional zone, and a relatively straight tangential zone downcoast. For embayed beaches, the degree of curvature (i.e., indentation ratio) has significant implications for littoral cell circulation, which mediates both cross-shore and alongshore sediment transport. This study investigated the longshore and cross-shore sediment distribution and profile sequence for Freshwater Beach in central Queensland, Australia. Freshwater Beach is a 10 km long macro-tidal embayed beach, located within the Shoalwater Bay Training Area. The beach is subjected to a mean tidal range of 6 m and prevailing onshore-directed winds and swell from the southeast. A total of 12 topographic profiles at ~1 km spacing were taken along the entire length of the beach to characterize variation in beach slope and foredune height. Sediment samples were collected along each transect for detailed grain-size and geochemical (XRD/XRF and SEM) analysis. Additionally, terrestrial LiDAR surveys were collected adjacent to topographic profiles for comparison with aerial-based LiDAR surveys. Preliminary results from topographic profiles show that the largest foredunes are located in the central portion of the beach, contrary to most embayed beaches where the largest dunes are typically located downdrift of the headland. Along the exposed section, the foredunes are large (~15 m high) and are hypothesized to be supplied by onshore welded bars that act as a sediment source. Presently the alongshore and cross-shore sediment exchange is unknown and the dynamics of surface drainage and freshwater seeps in close proximity to the outlet of Freshwater Swamp remain a priority for understanding the morphologic evolution of the beach-dune system. Ongoing research is currently in progress to address relationships between grain-size grading alongshore and foredune height to determine a sediment budget from the nearshore extending through the parabolic dunefield.