Located in the transistion zone between highland and Mekong delta, HCM city has an average elevation of 0.0 to 2.0 m. In the Southeast, the city is boundered by the sea with a coastline of 30 km. Thus, HCM city often suffered from inundation especially in the rainy season and tide high period. Land subsidence possibly resulted from groundwater over-extraction had been doubted since some manifestations of ground surface sinking were observed at the well fields in the districts No. 6 and Binh Tan in 2004. The common way to investigate land subsidence is to construct a network of monitoring stations to record two main parameters, i.e., settlement and pore pressure change. There are a few land subsidence monitoring stations that have been installed in HCM city since 2005. However, these monitoring data have not been available for public information. Due to the lack of studies on land subsidence, there are different opinions about the causes of subsidence in HCM city. Some scientists considere that groundwater extraction is the main cause of land subsidence, while others are in favour of natural self auto-compaction of the young soft clay sediment due to construction loads. Therefore, it is necessary to understand thoroughly land subsidence due to groundwater extraction. This study, the theory and methodology to calculate land subsidence due to groundwater extraction for HCM city using 1D FEM consolidation method, the TZP computer package, based on hydrogeological and geotechnical data. Initial calculated results for the central area of HCM city with the drawdown data taken from monitoring period of 1999-2009 show that land accumulative subsidence due to groundwater extraction could be as much as 63.8 cm, 85.2 cm, and 97.6 cm for 2010, 2040, and 2100, respectively.
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