Dam portfolio risks—a few definitions

Dam portfolio risks—a few definitions aims to bring clarity on terms definitions that oftentimes remain shrouded in mystery.

Risk Framework

Risk analysis frameworks provide a methodological basis for establishing a transparent and defensible evaluation of the risk generated by a given dam and/or portfolio of dams. They can be qualitative, semi-quantitative or fully quantitative. The framework is essentially a repeatable evaluation scheme which may rely on:

• quantification of expert judgment,
• subjective probabilities,
• empirical/statistical observations or
• probabilistic models (Stamatelatos et al. 2011; Ang, Tang, 1984).

Risk definition

Risk R has been historically expressed as p_f * C in many industries and areas of knowledge although some authors (Slovic, 1987; Loosemore et al., 2012) have attempted to introduce more complex structures.

Any efficient portfolio risk management (mitigation) effort of dams should be developed following an “enterprise risk management” logic (Jaafari, 2001), and not only a p_f reduction logic. Indeed, looking at only one part of the risk, for example, only at the probability or only at the consequence leads to wasting or mis-allocating limited resources (Chowdhury, Flentje, 2003). Thus, to optimize a dam portfolio mitigation approach, one has to combine p_f and the cost of consequences C to obtain the risk R. Consequences are sometimes considered as complex functions of physical and perceived losses (Loosemore et al., 2012).

ISO 31000: 2018(en) Risk management — Guidelines. 2018.

ISO defines risk as “the effect of uncertainty on objectives”. People often time forget that establishing the context allows to define the objectives. So, they skip this important phase. If one defines the system to be analysed, then considers probabilities as a measure of uncertainty and the effect on objectives as the consequences, then the technical and ISO definitions coincide. Thus, for example, the dam system represents the context, then one can state the objectives (no catastrophic failure?). Finally, in technical terms, the risk generated by a postulated dam breach results from the combination of the probability of occurrence of that breach and the loss of lives and all the other dimensions of the consequences, e.g.:

• environmental,
• business losses,
• H&S and finally
• reputational,
• etc.

Model and data uncertainties intervene on both the probability and consequence terms. Indeed, model and data uncertainties may include ignorance of real data and conditions (mechanisms and potential causes of failure) at the moment of the analyses or throughout the life of the structure, since inception of the project.

Dam Hazards

Hazards are the events or conditions generating potential losses. A long list of potential hazards may include for example:

• meteorological conditions,
• human error, human factors (normalization of deviance);
• poor management (lack of controls of water balance for example),
• poor design (inadequate drainage) and finally
• engineering arrogance (lack of appreciation of mechanisms that trigger failure (Hartford, Baecher, 2004; ICOLD Bulletin 121, 2001).

Closing remarks

At Riskope we maintain a glossary  which you can freely use and download. The terms we discuss in Dam portfolio risks—a few definitions are part of the next update.

There will be more in our next book which will help to identify and describe those risk assessment approaches and risk management practices we must implement in order to develop a path forward to reach societally acceptable risks.

Tagged with: dam hazards, dam portfolio, dams failures, ISO 31000, Risk definition, risk framework

Category: Consequences, ORE2_Tailings, Risk analysis, Risk management