Evaluating the decision criteria for the prioritisation of South African dams for rehabilitation in terms of risk to human lives

[摘要] ENGLISH ABSTRACT: In South Africa a large number of dams owned by the Department of Water Affairs (DWA) need tobe rehabilitated. This study investigated the decision process involved in the prioritisation of damsfor rehabilitation. DWA developed a risk analysis methodology for defining the risks associated withdam safety, expressed as the combination of the probability and consequences of dam failure. Theserisks are evaluated usingmultiple acceptability criteria to assess risk to human life and the economic,social, socio-economic and environmental impacts of dam failure. In this study, the criteria used inthe decision process to evaluate the acceptability of life safety risks were evaluated by comparingto international best practice methods, where the acceptability of risk to human life is commonlyassessed as the expected number of fatalities against life safety criteria presented as FN-criteria onan FN-diagram.Damrehabilitation should reduce the probability of dam failure, thereby reducing the risk to societyin terms of the expected lives lost. However, the rehabilitation works come at a cost and the levelof these investments are usually large. In addition, the rehabilitation of South African governmentowned dams are financed by society and these financial resources are limited. Thus investments intodam rehabilitation works should be worthwhile for society. Society's Willingness to Pay (SWTP) forsafety was applied to South African dam safety to determine the acceptable level of expenditure intolife safety that is required by society.Investments into improved safety levels are not always dictated by society, but could also bedriven by the decision maker or owner requiring an economically optimal solution for the rehabilitation.Economic optimisation accounts for considerations additional to life safety, including economicmotivations, damage costs of dam failure as well as compensation costs for lives lost. Ofteneconomic optimisation would govern the decision problem. Also, the DWA current evaluation does not take the cost of rehabilitation into account in any way. Thus, FN-criteria that primarily evaluateslife safety, but also incorporates a measure of economic efficiency, were suggested in this study.

[发布机构] Stellenbosch University