ABSTRACT:

An assessment of rockfall risk and control options for the Burleigh Head National Park, Queensland is presented. The park consists of a headland which rises from a basalt boulder beach to a rain forest covered plateau approximately 70 m above sea level at a slope inclination of 35o to 45o from horizontal. The basalt cap, which forms the plateau, is columnar jointed with the columnar blocks typically 1 m in diameter and 1.5 to 3 m long. Columnar boulders from the plateau occasionally fall, bounce, roll and slide down the lightly vegetated slope towards the beach with some of the boulders landing on or passing the Ocean View Circuit walking track near the base of the slope. Many of the recent rockfalls have occurred during or immediately after an intense rainfall event or period of prolonged rainfall. A quantitative assessment was undertaken to determine the risk to people walking along the Ocean View Circuit being struck by rockfalls and the risk reduction capabilities of various remedial work options. Probabilistic analysis of rockfall trajectories was undertaken using the computer programme ROCKFAL3 to produce distributions of boulder kinetic energy, bounce height and stopping distance relative to the walking track. Both total annual risk and individual risk were calculated. Risk levels were compared with various published acceptable risk criteria to determine if remedial action is warranted.

INTRODUCTION

A rockfall risk assessment has been undertaken for a portion of the Ocean View Circuit walking track in Burleigh Head National Park on the Gold Coast, Queensland. The Queensland Parks and Wildlife Service (QPWS) commissioned an investigation to quantify the risk of a falling rock striking a pedestrian walking along the track. The feasibility and cost of constructing rockfall containment structures to reduce the level of risk to an acceptable level was also investigated.

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