According to a report released by the Ministry of the Environment (MOE) in December 2004, the total area of land subsidence of two centimeters or more across Japan in fiscal 2003 was the least recorded since the survey started in 1978.

The greatest amount of subsidence at any once spot was 4.2 centimeters, recorded in Minamihama Town, Ishinomaki City, Miyagi Prefecture in northern Japan. Subsidence of two centimeters or more was observed in five other districts, totaling an area of 3 square kilometers. This was very much less than the 461 square kilometers recorded in FY2002.

Although land subsidence is triggered for various reasons, it is often caused by lowered groundwater levels and shrunken clay layers resulting mainly from excessive groundwater pumping. In the two areas where there was ground subsidence of 2 cm or more, the Niigata Plain in Niigata Prefecture and the Kujukuri Plain in Chiba Prefecture, about 50 million cubic meters of groundwater has been pumped annually to extract natural gas.

Both the national government and local authorities in Japan have been implementing measures in accordance with relevant guidelines, including restrictions on groundwater pumping, in order to prevent land subsidence. Also, a Directory for Environmental Information on Ground and Soil containing information about land subsidence, groundwater levels and regulations on groundwater management is available on the MOE website.




Posted: 2005/03/30 10:33:19 AM
Japanese version

TAG Energy , Food/Water , Government , Other , System/Law