At least 43 percent of Japan 's coastline is lined with concrete seawalls or other structures designed to protect the country against high waves , typhoons or even tsunamis . During the 2011 Tōhoku earthquake and tsunami , the seawalls in most areas were overwhelmed . In Kamaishi , waves surmounted the seawall — the world 's largest , erected a few years ago in the city 's harbour at a depth of , a length of and a cost of $ 1.5 billion — and eventually submerged the city center
2011 Tōhoku earthquake and tsunami
2011 Tōhoku earthquake and tsunami
Seawall