Resumen
Communication on the operation of a dam is crucial in evacuating residents before downstream flooding occurs. This paper examines the effect of communication regarding dam operation on evacuation, studying the case of the 2018 flooding of the Hijikawa River in Japan. After confirming the communication process and the messages of warning, we conducted a questionnaire survey of affected residents. The findings of the survey are as follows. (1) The discharge warnings issued by dam operators had no effect, because few people heard the warnings and even those who heard them were not inclined to evacuate. (2) Accepting the notifications from dam operators, local governments issued evacuation instructions. These instructions promoted evacuation. The most effective trigger of evacuation was route alerting by the volunteer fire corps. Information from dam operators induced the issuing of evacuation instructions, which activated the route alerting, and the information therefore indirectly promoted evacuation. (3) The Public Warning System operating on mobile phones had a certain effect in disseminating evacuation instructions where the system was used. (4) The messages issued here had insufficient specificity and clarity. A flood simulation considering the discharge flow of a dam needs to be conducted in addressing this issue.