2013 Volume 122 Issue 6 Pages 992-1009
Land transformation in Tokyo and its surrounding regions is reviewed, focusing on reclamation and cut-and-fill during the past several decades. The transition of the land transformation area is estimated using “Municipalities Area Statistics,” topographic maps, and geomorphological mapping data of the Geospatial Information Authority of Japan.
Before 1965, reclamation sites were located in Tokyo, Kawasaki, Yokohama, and central Chiba. These areas developed as industrial areas with major trading ports. From 1966 to 1975, the peak period of rapid economic growth in Japan, large areas were reclaimed in the Kawasaki, Yokohama, and Chiba-Sodegaura coastal areas. The land reclaimed during these periods, most of which was connected to old land, has mainly been used to site heavy industries. Since 1976, construction of artificial islands has been the dominant form of land reclamation. From 1976 to 1980, reclamation on a smaller scale than the previous period was carried out mostly between Tokyo and Chiba, not to make industrial sites, but to make business, commercial, residential, and leisure sites. Since 1981, there has been very little reclamation, with the exception of the expansion of Tokyo (Haneda) International Airport.
In upland areas, artificially transformed land comprises approximately 20% of the total land, and the increase since the 1980s has been small, while a large part of hill areas was transformed into cut-and-fill mosaic forms mainly in the 1960s and 1970s. Most of it was done to supply residential sites that supported population concentration in Tokyo and its surrounding regions. Many cases were of large-scale land development tied to the opening of new railway lines and stations. At present, artificially transformed land accounts for 56% of the total land in the Tama hills.
Land transformation affects the natural environment. Reclamation works sometimes cause water pollution and ground subsidence. To mitigate influences on the environment, artificial beaches were made to recover and sustain coastal ecosystems, and provide places where people could relax.
Land transformation also significantly influences natural disaster vulnerability. It is obvious through experiences of major earthquakes in the past several decades that reclaimed land is subject to liquefaction damage. Increases of inundation damage to valley-bottom part of hill areas at times of heavy rainfalls have resulted from residential land development. Fill-up ground is easily deformed by the strong motions of earthquakes.
Consequently, it is important to understand the history of land, no matter where it is located.
