Slopes pose a potential hazard to urban development. The risk analysis of the probability of fatality occurrence (or probability of loss of life) resulting from natural landslide or rockfall is based on five probability parameters of rain, slope failure/ rockfall, elements at risk, impact significance (i.e. death, injury and property loss) and fatality occurrence. The probability of occurrence and other factors such as value of life, design lifetime and costs of implementing measures can be used to assess the cost-benefit of the proposed mitigation measures. The cost-benefit analysis demonstrates that from an economical point of view, risks should be reduced until the marginal cost of measures is equal to the marginal benefit to be protected.