Risk assessment for dam safety - A framework for understanding

What risk analysis or risk assessment means to an individual often depends on where they first encountered it's use. It could have been used as a label for a rigorous mathematical treatment of test data or as a presentation of factors on which a decision on alternatives for remediation of a dam was made. Its use may have been termed risk analysis, decision analysis, risk management, hazard analysis, statistical analysis or some variation thereof. Risk applications and terminology extend from a detailed statistical evaluation of the value of a parameter (e.g. - concrete strength) to a decision by a major company on whether or not to take on a new venture. But what is it - Really? Lack of understanding of the differences between the processes used in various applications and strong perceptions of the potential for misuse of the results have left some doubting about the use of risk assessment as a viable tool to aid in making dam safety decisions. In this paper a framework for understanding dam safety risk applications and related terminology is provided. The processes applicable to dam safety are described and their roles in the engineering analysis phase, dam safety evaluation phase, and program management phase will be outlined - including: (1) a description of the key elements in a risk analysis, (2) a discussion of how risk assessment and risk management are applied, and (3) an explanation of the interrelationship between these three tools. The critical importance of failure mode evaluations and engineering judgment as an integral part of risk assessment and risk analysis will be stressed and specific value added elements of the process will be identified. Utilization of risk assessment with or without decision criteria will also be described. Finally, some reasons that concerns about the use of risk analysis as an engineering tool and as input to dam safety decisions have arisen and how those concerns might be allayed will be discussed.