Abstract
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.
Highlights
In July 2018, wet air from the south generated heavy rainfall in western Japan
Problematic, the Public Warning System (PWS) was useful in disseminating evacuation instructions in Ozu
The local government in Seiyo did not use the PWS as they considered the PWS problematic, the PWS was useful in disseminating evacuation instructions in Ozu
Summary
In July 2018, wet air from the south generated heavy rainfall in western Japan. In the city of Seiyo, rainfall registered 347 millimeters per 24 h (JMA, 2018) [1]. The inundation began soon after a discharge operation of two dams on the Hijikawa River. This paper examines the functions of and problems relating to information provided by dam operators for the evacuation of residents during the July 2018 flooding of the Hijikawa River. Sorensen and Sorensen (2006) [7] summarized the results of research conducted in the United States on factors that affect the responses of people They cited the residents’ knowledge of hazards, personal warning channels, frequency of warnings, message consistency, message certainty, and source credibility as factors that promote evacuation. It is important to investigate the residents’ reactions toward warnings of the 2018 flooding of the Hijikawa River as a case study of an actual disaster
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