15.9 Defining Operational, Tactical and Strategic Risks
255
Tolerance
Fig. 15.11 Mitigation on dam 4 effects on risks
immediate action would be the best course. Any action cited above would lead to the
black arrow in Fig. 15.11.
We will also note that Dam 3, with the highest tolerable risk of the portfolio,
could be mitigated under operational conditions, and that this mitigation would serve
operational goals as well as the tactical ones described in the next section.
15.9.2 Tactical Risks
The interdependencies of Dam 2 on Dam 3 can be lowered below tolerance by
effecting some kind of mitigation on Dam 3 that would change the likelihood of
its failure in case Dam 2 failed. An example of such a mitigation is an armored toe,
preventing erosion of Dam 3, after careful consideration of the liquefaction potential.
Such a mitigation would be perfectly in line with the negligence test result, leading
to a tactical investment of a few million dollars per year. Here again the portfolio
risk assessment makes it possible to allocate resources and avoid paralysis caused
by analysis and feeling overwhelmed (Fig. 15.12).
15.9.3 Strategic Risks
Dam 1B is considered intolerable independently of possible implementable mitigations (the black arrow in Fig. 15.13 remains above tolerance all the way down to the
human credibility threshold). Dam 1B therefore represents a strategic risk; i.e., only
an alteration of the system would make it tolerable (red arrow). Possible solutions
255
Tolerance
Fig. 15.11 Mitigation on dam 4 effects on risks
immediate action would be the best course. Any action cited above would lead to the
black arrow in Fig. 15.11.
We will also note that Dam 3, with the highest tolerable risk of the portfolio,
could be mitigated under operational conditions, and that this mitigation would serve
operational goals as well as the tactical ones described in the next section.
15.9.2 Tactical Risks
The interdependencies of Dam 2 on Dam 3 can be lowered below tolerance by
effecting some kind of mitigation on Dam 3 that would change the likelihood of
its failure in case Dam 2 failed. An example of such a mitigation is an armored toe,
preventing erosion of Dam 3, after careful consideration of the liquefaction potential.
Such a mitigation would be perfectly in line with the negligence test result, leading
to a tactical investment of a few million dollars per year. Here again the portfolio
risk assessment makes it possible to allocate resources and avoid paralysis caused
by analysis and feeling overwhelmed (Fig. 15.12).
15.9.3 Strategic Risks
Dam 1B is considered intolerable independently of possible implementable mitigations (the black arrow in Fig. 15.13 remains above tolerance all the way down to the
human credibility threshold). Dam 1B therefore represents a strategic risk; i.e., only
an alteration of the system would make it tolerable (red arrow). Possible solutions