Report on Damage Situations by Tsunami Propagation in River Channels and its Overtopping from Embankment in Great East Japan Earthquake

[出版社版]The tsunami caused by the Great Japan Earthquake at 14:46 JST on 11 March 2011, with a magnitude of 9.0 and epicenter 129 km east of Sendai, broke most of the sea embankment and coastal vegetation belt and caused catastrophic damage to people and buildings in the Tohoku and Kanto districts of Japan. A field survey was conducted to elucidate the damage situation of residential region by tsunami propagation in river channels and its overtopping from embankment. Abukumagawa River, Nanakita River and Old Kitakamigawa River located on Miyagi prefecture were selected for field investigation. In Abukumagawa River and Old Kitakamigawa River, overtopping flow from embankment occurred mainly at the outer-bank side of meandering section. Severe erosion was occurred on levee slope and neighboring houses were washed out by the scouring due to the overtopping flow. The hinterlands of coast and river had tsunami from two directions, coast and river, and the damage situation including the evacuation action for people became complex. Therefore, it is necessary to elucidate the location where tsunami is easy to be overtopped for different tsunami conditions