Assessing Rockfall Along the Illawarra Escarpment

Abstract

In recent years there have been numerous rock falls from the sandstone capped Illawarra Escarpment near Wollongong, Australia. As part of the ongoing Landslide Research project at the University of Wollongong, several of these events have been mapped in detail, including the volume and location of 348 individual boulders. These three rockfall sites have formed the basis of an escarpment rockfall modeling and susceptibility zoning project outlined in this paper. Using these detailed, site specific, evidence based mapping and high resolution GIS data, 2D Rocfall (Rocscience Inc.) computer models have been developed to simulate the real sites. This work has resulted in the development of a database of relevant geotechnical parameters for rockfall modeling along the escarpment. With this parameter dataset in hand, 3D rockfall modeling using the University of Alberta Rockfall Analyst extension for ArcGIS has been employed to aid in the development of rockfall Susceptibility zoning areas across the three subject field sites. Spatial density (Susceptibility) of the modeled rockfall trajectories provides a useful zoning outcome which compares favorably with the mapped rockfall boulders. This work has been completed which now forms the foundation for the rockfall modeling of the entire escarpment length over the next 12 months.