Coastal Damages in Ibaraki and Chiba Prefectures due to 2011 Tohoku Pacific Ocean Tsunami

Abstract

A post-tsunami survey was conducted to clarify impacts of the 2011 Tohoku Pacific Ocean tsunami on sandy coasts of Chiba and Ibaraki prefectures. The measured tsunami height varies from 4 to 8 m above the mean sea level at respective sites and shows a general tendency to slightly decrease southward. Analysis of tide data from nearby stations reveals that tsunami waves of same amplitude repeatedly attacked the coasts for several hours. A large portion of the coasts was protected from the tsunami by seawalls and/or high vegetated dunes while some areas without dunes or around river mouths were severely damaged by tsunami floods. Detailed damage analysis was carried out for some representative locations on the basis of high-resolution topography data.