188
13 Tolerance and Acceptability
13.1 Historic Tolerance Thresholds
13.1.1 Examples of Constant-Value Acceptable
and/or Tolerance Thresholds
Looking back in time various authors (Wilson 1984; Comar 1987; Renshaw
1990) defined simple societal constant-value risk acceptability criteria, as shown
in Table 13.1.
For landslides the Australian Geomechanics Society Suggested tolerable loss of
individual life risk as shown in Table 13.2 (AGSLT 2007).
13.1.2 Examples of Acceptable- and/or Tolerance-Threshold
Curves
Countless curves have been developed for different industries/hazards. In log-log
scale these curves appear as straight lines, thus “in real life” they have a hyperbolic
shape. Let’s immediately remark that in a log-log graph a straight line of slope −1
(−45°, i.e., going from p = 10
−4 to C = 10,000 = 10
+4 ) corresponds to a centred
hyperbolic function of constant risk. That would be the tolerance curve of a “rational”
being who does not feel any emotion toward small but extremely likely losses (the
“pain in the neck” type of maintenance nuisance) or very large losses at very low
likelihood (say the Fukushima type of phenomenon). As the mathematics have not
Table 13.1 Historic societal constant value risk acceptability criteria
Author
Units
Unacceptable risk/upper
bound
Negligible risk/lower
bound
Renshaw
Probabilities of fatality of
one individual per year of
exposure to the risk
10 −5
10 −7
Comar
10 −4
10 −5
Wilson
10 −3
10 −6
Renshaw
Probabilities of fatality of
ten individuals per year
10 −5
10 −7
Table 13.2 AGS suggested
tolerable loss of life
individual risk
Situation
Suggested tolerable loss of
life risk for the person most
at risk per year
Existing slope/existing
development
10 −4
New constructed slope/new
development/existing landslide
10 −5
13 Tolerance and Acceptability
13.1 Historic Tolerance Thresholds
13.1.1 Examples of Constant-Value Acceptable
and/or Tolerance Thresholds
Looking back in time various authors (Wilson 1984; Comar 1987; Renshaw
1990) defined simple societal constant-value risk acceptability criteria, as shown
in Table 13.1.
For landslides the Australian Geomechanics Society Suggested tolerable loss of
individual life risk as shown in Table 13.2 (AGSLT 2007).
13.1.2 Examples of Acceptable- and/or Tolerance-Threshold
Curves
Countless curves have been developed for different industries/hazards. In log-log
scale these curves appear as straight lines, thus “in real life” they have a hyperbolic
shape. Let’s immediately remark that in a log-log graph a straight line of slope −1
(−45°, i.e., going from p = 10
−4 to C = 10,000 = 10
+4 ) corresponds to a centred
hyperbolic function of constant risk. That would be the tolerance curve of a “rational”
being who does not feel any emotion toward small but extremely likely losses (the
“pain in the neck” type of maintenance nuisance) or very large losses at very low
likelihood (say the Fukushima type of phenomenon). As the mathematics have not
Table 13.1 Historic societal constant value risk acceptability criteria
Author
Units
Unacceptable risk/upper
bound
Negligible risk/lower
bound
Renshaw
Probabilities of fatality of
one individual per year of
exposure to the risk
10 −5
10 −7
Comar
10 −4
10 −5
Wilson
10 −3
10 −6
Renshaw
Probabilities of fatality of
ten individuals per year
10 −5
10 −7
Table 13.2 AGS suggested
tolerable loss of life
individual risk
Situation
Suggested tolerable loss of
life risk for the person most
at risk per year
Existing slope/existing
development
10 −4
New constructed slope/new
development/existing landslide
10 −5