Submarine topography and sediment distribution after the 11 March 2001 tsunami impact in Kesen-numa Bay, Miyagi, Japan

In Kesennuma Bay, the study area, the sea bottom was scoured, the geography and sediments were altered, and much debris, oil, and chemical materials flowed into the sea from land as a result of the 2011 0311 tsunami. Highly precise information for the change of geography and sediment distribution by this tsunami applicable to the reduction of tsunami damage can be obtained by this investigation. We collected data on water depth, refraction intensity by acoustic systems, and photographs by AUV and video films by ROV. We evaluated the marine environmental change based on a comparison with a chart published before this earthquake. The data suggest that the geographical changes by impact of the tsunami restricted to the inner bay and Ohshima strait, and much debris and clastic particles were transported and the dune was formed by the tsunami's backwash.