Objective To quantitatively evaluate the effect of seawalls on tsunami evacuation departure.
Methods A mixed-effect Cox proportional-hazards regression model was applied to evacuation behavioural data obtained from a probability survey of survivors of the 2011 Great East Japan Earthquake and Tsunami in Iwate and Miyagi prefectures.
Findings Presence of a seawall higher than the forecast tsunami height at any given time reduces the likelihood of prompt evacuation by 30%. Findings suggest the existence of a false sense of security among residents deriving from the presence of seawalls.
Conclusion Prompt evacuation is a key factor affecting survival. The effect of seawalls on evacuation decisions is an important policy consideration. More work is needed in disaster preparedness education and in the way tsunami warnings are given, taking into consideration the risk of forecast error. Priority should be given to promoting prompt evacuation and educating residents as to the uncertainty of tsunami forecasting, to ensure that residents do not ignore evacuation warnings due to false impressions of the safety provided by seawalls.
- Tsunami evacuation departure
- Great East Japan Earthquake
- natural disasters
- survival analysis
- false sense of security
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Contributors GTP conceived of the study and obtained the data. GTP, BT and SG conducted the analysis, wrote the first draft of the article and provided comments and revisions.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Survey data were provided by the Ministry of Land, Infrastructure, Transport and Tourism’s Reconstruction Support Survey Archive hosted by the Center for Spatial Information Science, The University of Tokyo. Data available at http://fukkou.csis.u-tokyo.ac.jp.