The potential use of individual and societal risk criteria within the Dutch flood safety policy (part 1): Basic principles

The Dutch government is in the process of revising its national flood safety policy. The current Dutch Flood Defense Act lays down design standards for the Dutch flood defenses. These standards have been based on/rationalized by economic optimizations in which investment costs are balanced against the discounted value of (potential) future losses. Loss of life is not considered separately. This paper presents the results of a research project that evaluated the potential roles of two risk metrics: individual and societal risk. These metrics are already used in the in the Dutch major hazards policy for the evaluation of risks to the public. Individual risk concerns the annual probability of death of an average, unprotected person. Societal risk concerns the probability of a multi-fatality event. This paper discusses technical aspects of the use of individual and societal risk metrics in flood risk management, as well as policy implications.