Applied Managerial Decision Analysis for Debris Flow Evacuation Decisions

Abstract

Since 2004, debris-flow evacuation implemented based on critical rainfall intensity for warnings of debris-flow occurrences has been a regulation in Taiwan, and its many implementations in recent years have proven successful. When deciding on the rainfall intensity associated with evacuation decisions, the social cost of debris-flow disasters should be taken into account in addition to the vulnerability of the area to such disasters. However, in current practical debris-flow evacuation processes, that cost is not considered. As such, the aim of this paper is to explore how rainfall intensity and social cost relate to the decision to evacuate ahead of a debris-flow. In doing so, decision-making and cost analysis methods commonly used in management science were employed to model a rationally simplified hypothesis and develop a systematic decision-making process regarding debris-flow evacuation. This process is influenced by uncertain parameters, such as typhoon-rainfall levels and debris-flow occurrences, and determined through statistical analysis; further, the value parameters of costs in terms of deaths and evacuation payments are also considered. Finally, the model thus developed was applied to a severe debris flow disaster simulation that occurred in Taiwan in 1990 for empirical testing. Results of this study suggest that the rainfall intensity and social costs are highly pertinent to decisions regarding debris-flow evacuation when considered from a financial perspective. Moreover, by quantifying the social costs of debris-flow evacuation through decision analysis, this study may help explain the relationship between the vulnerability of an area to disasters, the social costs involved, and the decision-making criteria. It may also provide scholars a better understanding of optimal strategies for the advancement of debris-flow disaster prevention.