Characteristics of damage due to tsunami propagation in river channels and overflow of their embankments in Great East Japan Earthquake

Abstract

The tsunami caused by the Great East Japan Earthquake on 11 March 2011, with a magnitude of 9.0, broke most of the sea embankment and coastal vegetation belt and caused catastrophic damage to people and buildings in the Tohoku and Kanto regions of Japan. A field survey was conducted to elucidate the damage to river embankments and their hinterlands (residential area) by tsunami propagation in river channels and overtopping of embankments. Two, three, and four rivers in Iwate Pref., Miyagi Pref., and the Kanto region, respectively, were selected for the field investigation. In the hinterlands, the tsunami came from two directions, coast and river, and the situation, including the evacuation of people, became complex. Therefore, it is necessary to identify locations of river embankments that can be easily overtopped by a tsunami in different tsunami conditions. Tsunami inundation patterns were classified by the river capacity and whether a river or sea embankment was breached or not. This will provide useful information for making new hazard maps and planning new cities.