Western Australia Chapter

Landslide risk management in the Coastal Limestones of Kings Park and Botanic Gardens, Perth

Bruce Bulley & Steve Easton

The coastal limestones along the Mount Eliza Escarpment in Kings Park, Perth, have a history of landslides and ongoing slope instability. With a major arterial road along its base, the escarpment has been the subject of a number of geotechnical and quantitative risk assessments. A programme of landslide risk management has been implemented by the Botanic Gardens and Parks Authority (BGPA). Slope instability along the Escarpment has developed largely as a result of man-made interference with the slopes, in the form of road cuttings, quarrying, logging, excavations and development, which date back to the early 1800’s. The main types of landslides consist of rockfalls and debris slides, with the principle trigger mechanism being rainfall. The weak and variably cemented limestones or aeolianites are subject to ongoing deterioration and erosion, which results in dynamic and continually changing slopes and development of unstable conditions.

To control and mitigate against the effects of the landslides, the BGPA has undertaken extensive remedial measures in the form of scaling operations, revegetation of the slopes, drainage control, review and modification of public access, underwalling, erection of rock catch fences, drape meshing of potentially unstable boulders and regular monitoring and inspection of the slopes. Remedial measures are undertaken in accordance with strict cultural heritage requirements and environmental controls. The presentation will review landslide risk assessment at Kings Park and the management and mitigation measures used to control them.

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