Disaster Resilience

Because our research focuses on the natural and man-made disruptions, we simply introduce the meaning and application of natural disaster resilience as following.

Different aspects of the concept of disaster resilience are currently being studied from a number of viewpoints within the academic research community. Many studies focus on the physical (technological) aspects of a system or the social (human) aspects of a system. But there is still significant discussion on combined human–environment interactions

(socio-ecological systems). (Zobel, 2011) Due to the diversity of perspectives presented in these different subjects, the concept of disaster resilience has developed a large number of different working definitions. (Zhou et al., 2010). We will not go into particulars here.

As mentioned before, the concept of resilience is related to the capacity of physical and human systems to respond to and recover from extreme events, and it has gained prominence in recent years as a topic in the field of disaster research (Bruneau et al., 2003; Rose & Liao, 2005).Resilience also can be thought of as an extension of the traditional concept of resistance, defined as the measures that enhance the performance of structures, infrastructure elements, and institutions, in reducing losses from a disaster. But while disaster resistance emphasizes the importance of pre-disaster mitigation, the concept of resilience needs to be extended in order to include improvements in the flexibility and performance of a system both during and after a disaster. (Falasca, 2008)

The definition of resilience from Subcommittee on Disaster Reduction (2005) is the ability of a community or system to adapt to hazards so as to maintain an acceptable level of service. Bruneau et al. (2003) also describe the resilience is the ability of social units such as organizations to mitigate hazards, to contain the effects of disasters when they occur and to carry out recovery activities in order to minimize social disruption and to mitigate the effects for potential future disasters.

As initially proposed by Bruneau et al. (2003), disaster resilience is characterized by four properties, which are robustness, rapidity, resourcefulness and redundancy. Zobel (2010) rewrites the meaning of them as following.

1. Robustness—the strength of a system, or its ability to resist the impact of a disaster event, in terms of the amount of damage or loss of functionality that results because of the event.

2. Rapidity—the rate or speed at which a system is able to recover to an acceptable level of functionality, after the occurrence of a disaster event.

3. Resourcefulness—the level of capability for dynamically responding to a disaster event, by identifying and implementing solutions to improve rapidity and/or robustness.

4. Redundancy—the extent to which components of the system are substitutable, and therefore able to be replaced or augmented when functionality has been lost or reduced.

Bruneau et al. (2003) also proposed the resilience triangle, which use the characterization of system performance to conceptualize of resilience illustrating in Figure1.

Figure 2.2 Original resilience triangle (Bruneau et al., 2003))

The community earthquake loss of resilience, R, can be measured by the size of the

expected degradation in quality over time (time to recovery). The mathematical expression is R = ∫ [100 − 𝑄(𝑡)]𝑑𝑡

𝑡₁

𝑡0

where Q(t) presents the quality of the infrastructure of a community at a given time t.

Performance at the vertical axis can range from 0% to 100%, where 100% means no degradation in service and 0% means no service is available. When an earthquake occurs at time 𝑡₀ , it could cause sufficient damage to the infrastructure such that the quality is immediately reduced. Restoration of the infrastructure is expected to occur over time until time 𝑡₁. At time 𝑡₁ , it is completely rebound to the former state.

This concept was adapted by Dorbritz (2011) to assess the disaster resilience of public transportation systems (Figure 2.3). He states that initial reduction of the system performance when a failure occurs can serve as a measure for robustness and redundancy. Rapidity impacts

the duration of recovery and resourcefulness can present the shape of the system performance curve after the event occurs.

Figure 2.3 System performance, degraded operation state and disaster impacts(R. Dorbritz, 2011)

Dorbritz (2011) thinks the resilience concept should consider prevention, intervention and recovery and divides the time period into three phases.

1. The prevention phase

This phase aims to increase the ability of systems to withstand the impacts of disastrous events on the system performance before such an event occurs. Systems should be designed in a way such they are maximally robust and the impacts on the system performance are

minimized

2. The intervention phase

In this phase, the organization tries to suggest appropriate strategies to positively

influence the disaster spreading process during the impacts of them. Catastrophe management and anticipating order of failures are example for intervention measures.

3. The recovery phase

After the occurrence of a disastrous event, large parts of the system may fail such that even the entire network might blockade. Recovery strategies try to regain operability as fast as possible. Usually, recovery measures induce much higher costs than preventive ones.

Experiences made in a recovery phase can be used to enhance the disaster resilience before a next occurrence. (Dorbritz, 2011)

Essential characteristics of resilience

According to above literature, we can sort out the relative properties of resilience from Murray-Tuite (2006), Tierney et al. (2007), Dorbritz (2011) and C. Ta el at. (2009) as the following table 2.2.

Resilience properties

Definition the application area

Robustness (Strength)

Ability of systems to withstand disaster forces without significant degradation or loss of performance

disaster resilience

System’s ability to withstand an event Cities resilience

Redundancy Extent to which systems are

substitutable, that is capable of satisfying functional requirements, if significant degradation occurs

disaster resilience

Availability of more than one resource to provide a system function

freight transportation system resilience Resourcefulness Ability to diagnose and prioritize

problems, to initiate solutions by identifying and mobilizing material, monetary, informational, technological

disaster resilience

and human resources

Rapidity Capacity to restore functionality in a timely way, containing losses and avoiding disruptions

disaster resilience

An acceptable level of service can be restored rapidly and with minimal outside assistance after an event occurs

Transportation network

Autonomous components

Parts of a system that have the ability to operate independently

freight transportation system resilience,

Cities resilience Collaboration Engagement of stakeholders and users in

a freight transportation system to promote interaction, share ideas , build trust, and establish routine communication

freight transportation system resilience

Information and resources are shared among components or stakeholders.

Cities resilience

Efficiency Optimization of input against output freight transportation system resilience,

Cities resilience Adaptability System flexibility and a capacity for

learning from past experiences

freight transportation system resilience,

cities resilience Interdependence Connectedness of components of a

system or the dimensions of a system, including the network of relationships

freight transportation system resilience

across components of a system, across dimensions of a system, and between components and dimensions

Table 2.2 The properties of resilience

We find the properties, autonomous components and interdependence, are a little contradictory. The property of autonomous components asks the system to operate independently. However, interdependence hopes that there is connectedness across dimensions of a system or components.