Consideration of life safety risk equity principles in the assignment of design flood probability

Abstract

ABSTRACT When designing hazardous infrastructure a life safety assessment process can be applied that considers three tests; 1 an individual risk equity test; 2 a societal intolerance test; and 3 a ‘legal’ test as to whether risks are reduced to be ‘so far as is reasonably practicable’ (SFAIRP) or ‘as low as reasonably practicable’ (ALARP). This approach, which is embedded in many workplace health and safety regulatory jurisdictions and safety standards for infrastructure including dams, nuclear facilities and industrial facilities, has clear justification, can be rigorously tested, and is defensible. While evidence to suggest a strong societal intolerance to floods is limited (i.e. there does not appear to be a disproportionate reaction to life loss from flood events compared to, for example, dam failure) there is a clear connection between flood risk and life safety equity principles. An individual life safety risk equity test, considering a person’s right to certain levels of protection in our society, compares flood risk with that of the background life safety risks from all hazards that exist in the Australian community. Based on age and gender distributed census data and typical annual exceedance probabilities assigned for flood management, there may be circumstances where flooding is the leading fatality risk for particular individuals living on a floodplain. Other considerations include ownership of flood risk (the floodplain manager or the individual), the distinction between voluntary and involuntary risk taking (noting that many road fatalities occur during flood events), the ratio between flood exposure and fatality (including flood hazard) and any legal and ethical obligations relating to public safety and a standard of care.