Effects of Ground Uplift, Construction of an Artificial Tidal Flat and Tsunami Seawalls on Marine Life and Local Residents Following the 2011 Great East Japan Earthquake

Eight years have passed since the Great East Japan Earthquake occurred. I divided the process of the earthquake into four main events—the initial earthquake including liquefaction, subsequent tsunamis, land subsidence and ground uplift—and examined the impact of each event on marine life. Under the influence of ground subsidence, the young oysters born in the summer of 2011 were attached 50 cm or more above where the parent generation was attached. However, in 2016, due to the influence of the subsequent ground uplift, oysters attached to the top of the rock began to die. Mass colonization of Manila clams occurred after the artificial tidal flat was created and the clam fishing industry was reopened. The new seawalls were constructed seaward of the previous seawalls; thus, the overall area of the tidal flat decreased. High seawalls also break the continuity of nature between land and sea. Plans are underway to separate the industrial area and the residential area bordering the seawall. From the point of view of disaster prevention, a high seawall is necessary, but it will cause great damage to tourism and residents’ lifestyles because the sea is hardly visible. In addition to population decline and aging, revitalizing the industry after construction of the seawall is a very difficult task. Finally, I briefly discuss the differences in response to disaster prevention by comparing cases in Asia and Europe with those in Japan.