Osamu Matsuo

Subsidence in the Noubi plains

This paper discusses a history of ground subsidence in the Noubi plains, which is one of the largest zero-meter areas in Japan, based on the past data on groundwater level and ground subsidence. Noubi plains span across the three Prefectures in the central Japan, namely Aichi, Gifu and Mie; they are alluvial plains located in downstream of the Kiso, Nagara, Ibi, and Syounai Rivers, with an area totalling about 1,485 km2. Results of analyses on correlation between the groundwater level and ground compaction revealed that after the groundwater levels turned for the rise, a decrease of 0.6 mm was observed in the monthly ground compaction for every 1.0 m of rise in the monthly average groundwater level. Thus, it is important to keep seasonal changes in groundwater level at a minimum in order to prevent ground subsidence, at the same time promoting the recovery of groundwater level.