Description & Background
“While relatively uncommon, dam failures continue to occur, sometimes with catastrophic consequences. Investigations of such failures have typically focused on the physical factors involved, which is understandable given the technical orientation and background of engineers. However, the creation and management of dams always involves interacting physical and human factors, and this broader dynamic system is responsible for both safety and failure of dams.
“Moreover, because physical processes are assumed to deterministically follow physical laws, with no possibility of physical ‘mistakes’, we can assert that failure of dams is ultimately always due to human factors. Traditionally, it has commonly been assumed that safety is the default for dams and other systems, and that failures are therefore due to atypical physical factors and/or egregious ‘human errors’. However, research over the past few decades suggests that this paradigm should be reversed, with the new default view being that a natural tendency is for systems to move towards disorder and failure (in line with the concept of increasing entropy), and with continual human effort thus being needed to maintain order and prevent failure.
"Moreover, because physical processes are assumed to deterministically follow physical laws, with no possibility of physical 'mistakes', we can assert that failure of dams is ultimately always due to human factors."
“This paradigm reversal leads to the question of why human efforts do sometimes fall short, allowing failure to occur. The most fundamental answer is that we humans, both individually and in groups, are highly fallible and limited. For example, our data and knowledge are incomplete, our models are unavoidably inaccurate to various degrees, our cognitive ability is finite (we have ‘bounded rationality’), we take heuristic shortcuts and settle for ‘satisficing’ rather than optimizing, we’re subject to a host of cognitive biases at individual and group levels, we forget things, and our intuition can be highly unreliable when dealing with unprecedented situations.
“As if all of this weren’t challenging enough, the norm is that we’re continually faced with finding appropriate tradeoffs between conflicting goals stemming from competing social, economic, political, professional, personal, and other pressures. For example, on one hand, we’re tasked with responsibility for safety, but on the other hand we face pressures to increase system efficiency, productivity, profitability, compliance with deadlines, competitiveness, etc.
“Studies in a variety of domains within and outside engineering have shown that major failures are usually preceded by a series of steps involving physical and human factors interacting over a relatively long period of time, often years or even decades. Dams are no exception to this general pattern. Each of these steps may be small, often small enough to go undetected or not elicit a response if detected (e.g., ‘minor’ seepage, erosion, or cracking), and with no step or factor sufficient by itself to produce failure. However, when enough factors accumulate and ‘line up’ appropriately, they can become jointly sufficient to produce observable incidents and failures.
“Assessment of the daunting challenges we face due to our limitations in dealing with complexity, uncertainty, and conflicting goals could be cause for pessimism. For example, ‘normal accident’ theory suggests that a substantial rate of major failures is inevitable for many kinds of complex systems. Yet, the empirical fact is that modern dam engineering has had a successful track record overall – in the US, there have been hundreds of dam failures among tens of thousands of dams – and the same applies in many other domains involving complex systems, including systems dealing with rapidly evolving adverse situations.
“Even in these challenging environments, organizations have been identified which have a long track record of success, thus becoming known as ‘high-reliability organizations’ (HROs). In general, HROs reduce rates of substantial failures by being preoccupied with avoiding failure. HROs are mindful, skeptical, cautious, and humble, actively searching for and promptly addressing indicators of trouble before problems grow too large, and making good use of all the information, expertise, and tools available to them to do so. Even with such traits, dam failures may not be entirely preventable, especially if we want continued innovation and progress, but we can still reasonably expect that shifting towards HRO traits – in our personal practices, our organizations, and the broader dam safety community – will significantly help reduce occurrence of failures."¹
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Additional Case Studies (Not Yet Developed)
- Vajont Dam (Italy, 1963)
- Ka Loko Dam (Hawaii, 2006)