Surprised by the Expected
The following excerpt is taken from a presentation at Singapore International Water Week on 10 July 2018. It was subsequently published in IWA’s H2Open Journal. Citation: Paul R. Brown, R. Shane Trussell; Moral dimensions of resilience in integrated urban systems: surprised by the expected. H2Open Journal 1 December 2018; 1 (2): 169–178. doi: https://doi.org/10.2166/h2oj.2018.011
RELIABILITY VERSUS RESILIENCE
First, we wish to make a clear distinction regarding the differences between the definition of ‘reliability’ (which describes a predicted risk of failure) and ‘resilience’ (which addresses performance during and after random extreme events – some resulting in system failures). Reliability predicts performance using well-established theories and probabilities to describe a distribution of future outcomes and their frequencies. It focuses on the performance of the system and its components. Resilience, on the other hand, addresses the performance and consequences of outcomes outside of those boundaries (defined here as extreme events). Resilience focuses on responses to conditions in the so-called ‘tail’ of possible future occurrences.
In fields of engineering, the mathematics of reliability and risk criteria is a well-developed discipline – largely grounded in assumptions of stationarity. It addresses
‘the solution of problems in predicting, estimating, or optimizing the probability of survival, mean life, or, more generally, life distribution of components or systems; other problems considered … are those involving the probability of proper functioning of the system at either a specified or an arbitrary time, or the proportion of the time the system is functioning properly’ (Barlow & Proschan 1996, p. xi).
The recovery capacity, costs, duration, and quality of life for the survivors is an externality in most of these decisions (optimistically assuming that life goes on).
Assessing the need for and resources required to ensure resilience under extreme conditions should consider the capacity of communities to endure and recover from those conditions. That capacity to recover varies greatly among communities and is often related to the availability of institutional and economic resources. For example, as surface water supplies disappear in Cape Town, South Africa it has been noted that wealthy communities are able to drill new wells, while the poor have no means to do the same. The traditional surface water storage and distribution system is failing for everyone, but the consequences of failure and the capacity to recover varies according to economic inequalities among communities (Sieff 2018).
The following example provides anecdotal evidence of both the potential inadequacy of traditional engineering modeling tools under extreme and compounding events, as well as the potential for these tools to inadequately inform the collaborative decision-making of independent organizations and infrastructure integrated into system-of-systems frameworks.
SURPRISED BY THE EXPECTED
Mudslides Kill At Least 17 People In Santa Barbara County Where Wildfire Scorched Hillside
The Montecito case illustrates the potential vulnerability of reliance on hydrological models that were developed and calibrated under assumptions of climate stationarity and acceptable aleatory risks. When two extreme events occur one after another, the uncertainties of compounding hazards suddenly introduce externalities (massive erosion combined with sediment and debris flows) that are not incorporated into the engineering modeling tools employed by decision-makers, public safety officials, and first responders. The case also illustrates the collaboration among agencies and institutions that share predictive tools and output during crisis situations. The integrated response illustrated in this case worked effectively to save lives during the wildfire event but was surprised by the consequences of a subsequent storm.
Montecito, California, is an affluent coastal community to the southeast of the city of Santa Barbara. During December of 2017, the massive Thomas wildfire burned through the Padres National Forest and stripped the watersheds draining to the coast of almost all of their vegetation. Fuelled by years of drought, the fire grew to become the largest wildfire on record in California's history. Fortunately, widespread mandatory evacuations during the fire prevented anyone in Montecito from dying, in spite of the loss of dozens of homes. Sadly, it was an intense rain event in January that killed over 20 people and injured many more. In advance of the storm, public officials issued warnings and encouraged voluntary evacuations. What transpired in the early morning hours of Tuesday, January 9 was a mudslide and debris flows that were described as ‘apocalyptic.’
In a front-page story on the mudslides published in the Los Angeles Times on January 13, 2018, reporters Matt Hamilton and Joseph Serna quoted Montecito Fire Protection District Battalion Chief Scott Chapman, who had reviewed planning maps prepared from data analyzed by the County of Santa Barbara prior to the storm. Those maps depicted 100-year and 500-year storm events and the flooding that could result. The Times reported:
‘Chapman said the flooding and flows foretold by the map are mostly accurate, with the exception of a small patch of homes by the 101 Freeway and Montecito Creek, which were not as flooded as the map would have predicted’ (Hamilton & Serna 2018, p. 7).
Then, the article went on to report the following statement by Battalion Chief Chapman, who said ‘Even expecting the worst and planning for the worst, no one expected this.’ This statement describes clearly and succinctly the fundamental problem faced by professionals in many dimensions of water management and technology.
The authors characterize this phenomenon as being ‘surprised by the expected,’ and Chief Chapman is not the only person who has experienced it – that is reliance on engineering analyses based on historical records that fail to predict the combined physical consequences of compounding extreme events; in this instance, an unprecedented wildfire followed quickly by an intense rain event. It is likely that surprises resulting from expected events that dramatically exceed expectations will continue to occur.
Addressing this issue following the unprecedented rainfall in Houston resulting from Hurricane Harvey, an editorial by Stanford earth system science professor Diffenbaugh (2017) published in the New York Times, implored policy makers to face reality and prepare for the unknown unknowns (aleatory uncertainties).
‘Refusing to acknowledge the changing odds of extremes means that we will be unprepared for events that fall outside of our experience. Denying climate science is not just a political statement. It also puts American lives and property at risk’ (Diffenbaugh 2017).
Is it realistic to prepare for ‘events that fall outside of our experience’ – is there a technological solution for that? In the engineering planning and design process, the answer is likely ‘no, not yet.’ The development of design criteria that protect the public from all possible events (including ones that have never happened in the past) is both wishful thinking and unaffordable – even if all of those contingent events could be dreamed up.
What is achievable is an explicit recognition of the likely consequences of catastrophic failure irrespective of the future cause, asking what happens after the failure of infrastructure and how long will it take to recover? The focus on protecting a community during a disaster and minimizing the time needed to recover from it, is the real meaning of ‘resilience.’ Eliminating, to acceptable levels of risk, the possibility of experiencing that disaster is the meaning of ‘reliability.’
