Today, I'm pleased to present a guest entry from SEED Ph.D. student, Vikram Rao. This article, an advance from Risk Analysis by Stephanie Chang and colleagues, is an exciting introduction to the use of expert judgment to investigate infrastructure resilience. Traditionally, expert elicitation is used to evaluate probabilities to assess the vulnerability of a critical system to outages of feeder systems or incidence of extreme exogenous events. In this article, Chang and colleagues emphasize the use of expert elicitation to assess such resilience quantities as time to recover and disruption to system services over time. I hope you enjoy this as much as I did, and thank you Vikram for your insights...
This article examines resilience of infrastructure systems using expert judgments. This is of interest since disasters such as earthquakes can cause multiple failures of infrastructure systems since they are interdependent. The approach here is to characterize system resilience, understand the relationships between interdependent systems in the context of resilience, and understand ways to improve resilience, which is of interest to risk managers. Many infrastructure systems are considered here, including water, electricity, and healthcare.
The researchers use expert judgments in a non-probabilistic approach. One goal is to elicit the service disruption levels, given as degree of impact/degree of extent, for numerous sectors. Interdependency diagrams show the dependencies between systems and provide clues as to the cascading nature of disaster events. For example, healthcare is heavily dependent on water, which tells health risk managers that it is advisable to have alternate water sources available in the event of emergency. One thing I find interesting is that there is no agreement on the extent of infrastructure reliance on water. Some studies claim that water is needed for other infrastructures to function, others do not. So the importance of water in infrastructure resilience remains to be seen.
When discussing the results, the authors bring up the fact that the representatives (experts) revise their judgments in the face of new information. Experts realize that the importance of a system is greater than originally believed, or that interdependencies exist that they had not considered. Since infrastructure systems are so interdependent and functional systems are critical for human well-being, the sharing of information between infrastructure systems is needed going forward.
One area I would like to see additional research is to explore resilience in water distribution systems, particularly looking at costs associated with disaster recovery and time to restore water distribution functionality. We could use expert judgments to examine the quantitative nature of water system resilience, for example eliciting the cumulative distribution of water functionality as a function of time (e.g. 25% water functionality restored after 1 week, 75% after 3 weeks). This is of course valuable to risk managers who are seeking to understand the nature of water system functionality in the wake of a disaster.