A concept for water-based community to sea level rise in the lower-lying land areas — Toward reconstruction of coastline area in disaster-stricken northeast Japan

Strenuous efforts have been made to restore the global environment and create a sustainable society. In spite of the widespread movement to diminish greenhouse gas however, a substantial result is still to be attained. Meanwhile, the situation has worsened for many rural residential areas and cities near sea and/or rivers, such as the tidewater region, faced grave danger. On Mar. 11, 2011, incredible disasters struck the coastlines of northeast Japan in the form of huge earthquakes and massive tsunami. A 10m-high breakwater, the strongest available at that time, was destroyed completely. We have now learned that whatever type of civil engineering structure is used, it is impossible to counter the immeasurable power of nature. In this paper, we propose a revolutionary concept for establishing innovative urban community bases in lower-lying lands. The living space is founded upon floating platforms riding the water in artificial inlets and/or lagoons, to realize a sustainable residential environment which ensures safety and prosperity. This paper presents concrete details as to the application of our concept to the proposed water-based urban community in the Kesennuma Harbor Area of northeast Japan. Using this concept plan was evolved for a floating city, with its economic efficiency having been evaluated; in addition, some engineering studies were conducted on assumption that an actual site in Kesennuma was to be redeveloped.