Uncertainties in the risk assessment of hydropower dams:state-of-the-art and outlook

Risk assessment of hydropower dams is a topic of great interest for countries with extensive production facilities like Switzerland. Due to the high costs associated to the detailed simulation of dam failure events, however, traditional approaches to quantify the risk they pose are largely based on the statistical analysis of historical data, or on worst-case scenario modelling. In the latter case, the design of such scenarios is usually based on sometimes contrasting expert opinion or very sparse available data. In addition, there exist no unique framework or set of tools to quantitatively assess the socio-economical consequences of a dam-related flood event. The sparsity of available data, combined with the variability of environmental conditions (e.g. weather conditions, time of the day etc.) and lack of knowledge on the failure process (e.g. dam failure mechanisms) create an additional layer of uncertainty that is not yet properly dealt with in the current risk assessment workflows. This report summarizes the state-of-the-art of risk assessment for hydropower production dams at all levels: from the problem statement itself, to the technical tools (theoretical and numerical) available for its solution, with a focus on life loss estimation and on the role of uncertainty on the final analysis results. The work for this report was conducted within the project “Risk Governance of Deep Geothermal and Hydro Energy” of the National Research Programme “Energy Turnaround”. It is closely coordinated with ongoing activities of the Technology Assessment group at the Paul Scherrer Institute (PSI) in both the National Research Program (NRP) 70 “Energy Turnaround” and the Swiss Competence Center for Energy Research (SCCER) “Supply of Electricity” (SoE).