ABSTRACT
The Roxburgh Dam in New Zealand floods the steep sided Roxburgh Gorge. Many very old large landslides occur in the gorge which is just downstream of the Clyde Power Project where major stabilisation works were carried out on similar landslides. Rapid landslide failure could dam the Roxburgh reservoir with serious consequences. Experience at Clyde and knowledge, insight and understanding of many processes related to geology, geomorphology, climate, vegetation, fauna and land management, have made a major contribution to a preliminary assessment of the risk of a serious rapid landslide at Roxburgh. The probability of formation of a landslide dam was estimated to be about 1 in 12,000 years. Current work at Roxburgh is aimed at achieving a better understanding of slope processes so that higher risk areas can be identified, monitoring targeted, and the risk can be managed. Acceptable or tolerable risk for the project has not been predefined. Some quantification in risk assessment is useful but the role of uncertainty and judgement must be acknowledged.
