Land subsidence at the Kujukuri Plain in Chiba Prefecture, Japan: evaluation and monitoring environmental impacts

The impacts of land subsidence on surface environmental changes were analysed for the Kujukuri Plain, Japan, where subsurface brine has been abstracted for more than 50 years. Reconstruction of past landforms using airborne laser scanning and existing levelling data showed that the geomorphological setting of the whole region, such as beach ridges and backmarshes, has been retained during the recent 40 years. Apparent and simple relationships between shoreline retreat and land subsidence were not recognized, and the spatio-temporal distribution of shoreline change seems to be mainly controlled by coastal constructions. In addition, a method to measure long-term deformation by combining InSAR and time series analysis was proposed to improve our ability for monitoring land subsidence. The local uplifts and subsidence detected by the proposed method were quite consistent with those obtained from levelling data, suggesting that our method was applicable to the detailed monitoring. By combining and integrating the approaches presented in this paper with numerical modelling of deformation/fluid flow processes, scientifically sound recommendations for the sustainable development of the subsurface resources can be proposed for society.