Reconnaissance report on damage in and around river levees caused by the 2011 off the Pacific coast of Tohoku earthquake

The gigantic earthquake on March 11, 2011, caused significant damage in and around river levees over a vast area. Because the amount of damage was on such a huge scale, emergency restoration was difficult and many lessons were learnt. The cause of the damage in most cases was liquefaction either in the foundation or in the levee body, and the latter was recognized as a new technical problem. Many levees in the coastal area experienced the combined effects of the tsunami with the co-seismic subsidence of the earth's crust. Among the many examples of damage, one positive issue was that damage mitigation measures such as drainage and soil improvement were found to be effective. The present text addresses the findings and lessons learnt from the authors' emergency activities after the quake.