Assessment of stability of an exposed microtidal beach, Western Tasmania

Abstract

Beach erosion is an increasing threat to the natural resources of many countries, and is expected to increase with rising sea-level. West Tasmania has extensive fetch from the circum-polar Antarctic Ocean, also located in the “Roaring Forties” latitudes. Beaches of this coastline previously studied have shown major erosion, attributed to recent relative sea-level rise as they are largely secluded from human impacts. This study assessed Four Mile Beach, located in the central section of the west coast using methods of spatial analysis 1952–2011, beach profile survey and sediment analysis. Results showed only minor erosion of the vegetation line to the north, and stability and progradation in the central and southern extents of the beach. Blowouts showed more major changes, with three large blowouts towards the south becoming parabolic dunes, and one in the north re-vegetating. Dune sediment was mostly rounded fine sand indicative of active aeolian processes, while seaward edge sediment was sub-angular with a 15–20% of carbonate content on most transects, indicative of a sediment supply from offshore. Ongoing coastal stability of this pristine coastline would be facilitated by continued monitoring, management of any potential human impacts, and control of any potential invasive species that may affect sediment budgets.