Rockfall Hazard Assessment at the World Heritage Site of Giant’s Castle Reserve, Drakensberg, South Africa

Abstract

Drakensberg is a steep, mountainous terrain, where rockfalls widely occur along the slopes of the V-shaped valleys. Rockfall events, often responsible for casualties and fatalities, have occurred in the past and occur sporadically in that mountain range. In this study rockfall accumulation zones were mapped, and a data set of 208 rockfall boulders was developed. The falling blocks’ measured size range from 1 m3 to 4 × 103 m3 and the shape for the majority of the blocks is either cube or prism. A good agreement between the measured cumulative distribution and a fit by a power-law distribution, for volumes larger than 20 and 50 m3 is noticed. The rockfall trajectory paths, maximum run-out distances, involved kinetic energies, and rockfall velocities were estimated, based on rockfall analysis. A pseudo 3D rockfall analysis based on the shadow angle principle was applied to account for the lateral disperse of the falling blocks. The outcome of the rockfall analysis revealed that Giant’s Castle Main Camp is susceptible to rockfall hazard.