Franco Oboni & Cesar Oboni


such deficiencies are generally the result of deliberate human choices (excessive audacity, errors and omissions, insufficient efforts)”. The 2016 paper[13]


therefore took a rather extreme, but logical line of thinking, stating that dams’


failures find, in the vast majority, their root-causes in human choices and not in natural events. At the center of this reasoning there is the concept of credibility threshold. Many industries consider the limit of credibility at around 1/100,000 to 1/1,000,000 (10-5


to 10-6 )[15,16,17,18]


so it can be stated that any


event above that limit is not an “Act of God” (or, following modern times buzz-words a “Black Swan”) and should be therefore foreseen/ planned for. It was also noted that, reportedly, most dam failures have occurred for other causes than “Black Swan” natural events, but again for “chains” of gradual deviances, which become “normalized” over time, stemming from investigations, design, construction, management and long-term monitoring. For the e-IDC four different functions (Geotechnical Investigations, Engineering, Construction, Management (including Water balance), Monitoring) constituting the chain of elements responsible for success/failure of a dam were identified. A “causalities network” was built as shown in Figure 1 using the same concept of a Bayesian network.


Figure 1. Functional scheme of the e-IDC with the hazards selected[13] Various hazards (root causes) are lurking on each element of Figure 1 such as, in the specific approach


adopted in that paper: Insufficient effort, Mistakes, Excessive Audacity, etc. leading to a probability of failure PoF for each element evaluated using a reliability model. Of course, the list of selected hazards should be discussed project by project. Failure modes previously identified in the literature, for instance ICOLD[19] from a 1910-2009 compilation[11]


due to the selected hazards were selected as:


• Slope instability; • Earthquake and mine subsidence; • Overtopping; • Foundation; • Seepage and structural.


184 | Dam Engineering | Vol XXXIII Issue 3


) and


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