Engineers Australia

Coastal rockfall hazard identification, Barwon Heads, Victoria

B. J. Muller, P. G. Dahlhaus and A. S. Miner

Abstract

An investigation of rockfalls at The Bluff, Barwon Heads, Victoria was undertaken as the initial component of a larger Risk Management study. Recent rockfalls are a concern for the management of The Bluff, which is a natural heritage asset and popular tourist destination. Subaerial erosion was found to be the predominant slope forming process with variations in slope morphology dependant on the presence of erosion resistant calcrete capping. Spatial variation of rockfall types is controlled by the orientation of bedding in relation to the slope face, and the development or presence of overhangs. Eight distinct modes of failure were identified. Significant changes in the morphology of the rock mass and sixty-three rockfall events were identified through the analysis of historical photographs, indicating active erosion at The Bluff over the past 100 years. Recent rockfall events have coincided with periods of high rainfall, which has been identified as a major trigger. Rock strength parameters and mechanical properties were determined by laboratory testing and the test results were used to investigate the failure mechanics. Back analysis of failed blocks has shown that that failure is influenced by larger scale rock mass features, rather than rock property strength.