GIS was used as one of the primary analysis tools during a rock fall hazard assessment and analyses of Chapmans Peak Drive, south of Cape Town. This paper describes the methodology used and the results of this work. Key methods used included 1) the development of a digital elevation model (DEM) used to delineate rock fall runout Zones; 2) rating Zones using an adapted version of the Oregon rock fall hazard rating system (RHRS) in order to determine the relative vulnerability of individual Zones to rock fall; 3) undertaking rock trajectory analyses to determine the distribution of kinetic energy for identified rock fall runout Zones; and 4) undertaking event tree analyses based on the synthesis of all data in order to establish Zones with the highest risk of fatalities. The results of this work shows that the vulnerability and risk varies considerably between Zones. The reasons for these differences are briefly elucidated.
Chapmans Peak Drive, located between Hout Bay and Noordhoek, on the Atlantic Ocean side of the Cape Peninsula, near Cape Town, South Africa (Fig. 1) is a favorite tourist route and is famous for its scenic beauty. The Drive, parts of which hug the near vertical mountainside of Chapmans Peak, is both a major tourist attraction and an important transportation link between the southern part of the Cape Peninsula and the city of Cape Town. At least 10 people have been killed and many more injured as a result of rock falls along parts of the drive, with the majority of the deaths or injuries having occurred within the last ten years. Subsequent to the death, and while the road was still closed, significant fires swept through the area, further destabilizing the slopes. In an effort to rehabilitate the