Understanding Hidden Risks from Disasters: Cases of Hurricane Katrina and Fukushima Nuclear Meltdown

Risks or uncertainties have been characterized in many ways and are fairly well understood, but hidden risks have been underemphasized. This study identifies characteristics of hidden risks, especially from disasters, and characterizes them on the basis of findings from past research. The proposed framework characterizes hidden risks by retrospectively asking four questions: What was unidentified? Why was it unidentified? What was uncertain? Why was it uncertain? The framework helps characterize the ambiguous nature of hidden risks, which were believed to be unidentifiable or even unimaginable. The cases explain how the proposed framework works for catastrophic disasters. (C) 2017 American Society of Civil Engineers.