7.1: Introduction
Infrastructure managers may go long periods of time without significant failures, extreme events or security breaches occurring for their infrastructure. However, a manager must be prepared to deal with such events and should plan ahead to mitigate the potential costs of such events. This chapter discusses approaches to prepare for and to mitigate the damages of such events.
The list of potential adverse events is long indeed:
- Critical infrastructure failure, such as electricity, water supply, telecommunications, etc.,
- Extreme events, such as earthquakes, fires, floods, hurricanes, landslides, lightning strikes, tornadoes, etc., and
- Security problems, such as bombs, guns, computer hacking, riots, etc.
News media regularly report such events throughout the world on a daily basis. Even the resignation or retirement of an employee with critical management knowledge can reveal a lack of resiliency in management.
While the chance of occurrence for any of these events is quite low in any particular year, the probability is typically not zero. The exception might be physically impossible occurrences such as flooding to a facility at the top of a hill (but then the top of the hill may be more prone to have high wind!). Figure 7.1.1 illustrates the estimates of probabilities of significant (magnitude greater than 6.7) earthquakes in California. The figure outlines the boundaries of California in white and the various earthquake fault lines show up as higher probability linear segments. The probability scale ranges from 10-6 (0.0001% chance per year) in blue to 10-2 (1% chance per year) in purple. While these particular estimates are uncertain, California infrastructure managers should be prepared for an earthquake event!
Even with a low probability of an event occurring, the number of repetitions of the underlying risk opportunity may result in a significant risk. For example, suppose your risk of falling from a scaffold is 0.1% in any particular day, which likely seems like a small risk to you. However, if you are on a scaffold 365 days a year, the probability of a fall over the course of a year would be (as discussed in Chapter 4):
\[P_{r}\{f a l l\}=1-P_{r}\{\text { no } f \text { all }\}^{365}=1-0.69=0.31\]
So you would have a 31% chance of a fall over the course of a year spent on scaffolding. Over fifteen years, the probability of a fall would increase to 99.6%. Similarly, riding a bike to and from work might have a low probability of experiencing a crash, but over a long period of time the likelihood of a crash increases. Better risk management might make changes such as safety straps on scaffolding or dedicated bike lanes. The result would be to lower the daily probability of an event considerably.
In addition to the chance of occurrence, the other dimension of risk management is to consider the severity of consequences for an event. A small flood may have some costs, but an organization could likely recover its infrastructure services rather quickly. In contrast, a large flood or a terrorist attack could have major consequences, including subsequent legal procedures. Similarly, small earthquakes or wildfires may have limited impacts, but a large earthquake or fire could require major rehabilitation or rebuilding.
Infrastructure managers should prepare for events with high frequency and low impact such as heavy rainstorms. For example, a large company with multiple oil platforms in the Gulf of Mexico should be prepared to secure and evacuate the platforms regularly due to hurricanes. But managers also need to prepare for high impact, low probability events such as earthquakes. Fortunately, high impact and high probability risks are rare. Also, low impact and small probability events are less of a concern than these other categories. Figure 7.1.2 illustrates the disruption probability and consequences for several organizational threats.
As an example, Figure 7.1.3 shows identified risks for water and wastewater systems.
Good infrastructure design and construction can significantly reduce the consequences of many risks. For example, earthquake resistant facility design has become required in earthquake prone areas. Similarly, adequate storm water systems (and good preventive maintenance) can reduce the risk of flooding.