JICA-RI Research Associate Presents Analysis on Subsurface Environment Changes at Joint Symposium by Japan Association of Geographic Space and JICA

In case of subsidence, the following indicators are used for the DPSIR analysis; population, income level, and industrial structure for “D”, groundwater volume and water consumption for “P”, groundwater level for “S”, subsidence for “I”, and countermeasures against subsidence for “R.” By looking into how these indicators change as urbanization advances, the study attempts to comprehensively grasp the degree of social and economic development as well as its effect on subsidence.

Toyota classified the characteristics of each city’s development over the approximately 100-year period into five phases according to urbanization stage, which are: “early stage of urbanization,” “industrialization,” “subsidence recognition,” “regulation,” and “settlement”. The analysis shows that ground sinking worsened considerably during the “industrialization” phase in many cities, when a large amount of groundwater was intensively pumped up. The study also clarified that only three cities -- Tokyo, Osaka, and Taipei -- have reached the “settlement” phase while a city like Bangkok has conducted countermeasures but the problem remains, and in those such as Jakarta and Manila, no effective countermeasures have been taken despite the recognition of the ground-sinking phenomenon.

Further, Toyota carried out comparative analyses of the seven cities, which revealed each city’s urbanization pattern and differences in environmental problems. In case of Jakarta and Manila, serious subsidence occurred because vast amount of groundwater was pumped in the rapidly growing urban areas due to their large populations and economic scales. Meanwhile, in Taipei and Bangkok, groundwater levels recovered relatively fast thanks to the abundant natural discharge of groundwater.

Toyota concluded the presentation, saying that: “Urban areas in developing countries, particularly in Asia, will face a sharp population rise in the near future. So it’s critical to take environmental measures applying the lessons of urban development process from the past. Environmental problems are complex. Therefore, it’s indispensable to conduct accurate monitoring, integrate monitoring and statistical data, and have a standpoint to shed light on the causality between development and environmental problems.”