11.7 Conclusion
The concept of vulnerability implies a measure of risk associated with the physical,
social and economic aspects and implications resulting from the system’s ability to
cope with the resulting event. Resilience implies the ability of a system to perform
properly even when placed under pressure or the ability of systems to absorb and
recover from the impact of disruptive events without fundamental changes in
function or structure.
Based on what is required to face disasters, features should be inbuilt in the
system (design, normal operation, etc) so as to offer better, if not complete, resilience
to the system. As resilience increases, the degree of damage for a given intensity
hazard decreases.
Measuring resilience is not easy as this depends on the system under study. It is
important to look at the ways resilience is being considered and use these as a
method to measure resilience, either qualitatively and quantitatively.
In most cases, the systems are rarely totally down. While qualitative assessment is
useful to understand how bad things are, quantitative measures give quantified
estimates of performance, time and effort (cost) that are more meaningful to
stakeholders.
System resilience is concerned with the protection of vulnerable people, and
probably poor as well. Providing resilience means providing a safeguard against a
certain risk. Hazards are more severe when the return period is a longer one. The
important issue relates to the level of protection that is considered desirable.
For example, rainfall frequency and intensity records can be used to estimate the
magnitude of rains and the ensuing flood flows. In this respect, it is important to note
that there is a 26% probability that a 100 year rain will occur during the next 30 years
(a generation).
In practical terms, this means that each generation has a 1 in 4 chance of
experiencing flooding, even if an exceptional rainfall intensity of 100 year has
been considered. Over a 75 year lifetime, the likelihood rises to 0.53, i.e., the
average person has a 1 in 2 chance of experiencing flooding during his lifetime.
Is the population ready to accept this? If no, what is the price to pay to have a safer
protection?
The issue of event probability also means that one thing is certain – the cost of
expenditure incurred, with possible benefits, in the way of cost avoidance, should the
disaster event eventually occur.
The development of the water supply network in a haphazard way brought
inherent vulnerabilities, which need to be removed gradually. Some resilience has
gradually been introduced into the system, sometimes at high cost. A cost benefit
exercise could be carried out to determine the feasibility of adding such resilience.
Measuring resilience is not easy as this depends on the system under study. It is
important to look at the ways resilience is being considered and use these as a
method to measure resilience, either qualitatively and quantitatively.
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11 Infrastructure Resilience
The concept of vulnerability implies a measure of risk associated with the physical,
social and economic aspects and implications resulting from the system’s ability to
cope with the resulting event. Resilience implies the ability of a system to perform
properly even when placed under pressure or the ability of systems to absorb and
recover from the impact of disruptive events without fundamental changes in
function or structure.
Based on what is required to face disasters, features should be inbuilt in the
system (design, normal operation, etc) so as to offer better, if not complete, resilience
to the system. As resilience increases, the degree of damage for a given intensity
hazard decreases.
Measuring resilience is not easy as this depends on the system under study. It is
important to look at the ways resilience is being considered and use these as a
method to measure resilience, either qualitatively and quantitatively.
In most cases, the systems are rarely totally down. While qualitative assessment is
useful to understand how bad things are, quantitative measures give quantified
estimates of performance, time and effort (cost) that are more meaningful to
stakeholders.
System resilience is concerned with the protection of vulnerable people, and
probably poor as well. Providing resilience means providing a safeguard against a
certain risk. Hazards are more severe when the return period is a longer one. The
important issue relates to the level of protection that is considered desirable.
For example, rainfall frequency and intensity records can be used to estimate the
magnitude of rains and the ensuing flood flows. In this respect, it is important to note
that there is a 26% probability that a 100 year rain will occur during the next 30 years
(a generation).
In practical terms, this means that each generation has a 1 in 4 chance of
experiencing flooding, even if an exceptional rainfall intensity of 100 year has
been considered. Over a 75 year lifetime, the likelihood rises to 0.53, i.e., the
average person has a 1 in 2 chance of experiencing flooding during his lifetime.
Is the population ready to accept this? If no, what is the price to pay to have a safer
protection?
The issue of event probability also means that one thing is certain – the cost of
expenditure incurred, with possible benefits, in the way of cost avoidance, should the
disaster event eventually occur.
The development of the water supply network in a haphazard way brought
inherent vulnerabilities, which need to be removed gradually. Some resilience has
gradually been introduced into the system, sometimes at high cost. A cost benefit
exercise could be carried out to determine the feasibility of adding such resilience.
Measuring resilience is not easy as this depends on the system under study. It is
important to look at the ways resilience is being considered and use these as a
method to measure resilience, either qualitatively and quantitatively.
330
11 Infrastructure Resilience