Tsunami inundation after the Great East Japan Earthquake and mortality of affected communities

OBJECTIVE: To examine the relationship between mortality rate and tsunami inundation after the Great East Japan Earthquake (GEJE) in 2011. STUDY DESIGN: Cross-sectional study. METHODS: One hundred and fifty-five town or village sections in Ishinomaki, Myagi Prefecture, were included in this study. Three areas in the city were classified by characteristic landforms: plains area (n = 114), ria coastal area (n = 27) and Kitakami riverside (n = 14). The correlation coefficient between tsunami inundation depth and mortality rate was calculated for each area, and the differences between the areas were examined. Furthermore, multivariate analyses adjusted for the characteristics of the sections were conducted using census data taken before the GEJE. RESULTS: An association was found between inundation depth and mortality rate for Ishinomaki as a whole (r = 0.65, P < 0.001), Kitakami riverside (r = 0.85, P < 0.001) and the plains area (r = 0.75, P < 0.001) in separate analyses. However, no association was detected between inundation depth and mortality rate for the ria coastal area (r = 0.14, P = 0.47). CONCLUSION: The ria coastal area has good accessibility to the hills and tight bonding between members of the community. These factors seemed to play crucial roles in the lower mortality rate in this area despite the deep inundation.