Assessment of long-term ground subsidence and groundwater depletion in Hanoi, Vietnam

Rapid urbanization and population growth in Hanoi city raise the demand for groundwater and the risk of land subsidence. This study is the first to conduct a long-term interferometric synthetic aperture radar (InSAR) analysis with different SAR sensors including ALOS, COSMO-SkyMed and Sentinel-1 to evaluate the spatiotemporal evolution of subsidence in Hanoi between 2007 and 2018. The results show that subsidence in Central Hanoi had been diminishing during these 12 years, while the southern and western outskirts (Ha Dong and Hoai Duc district) had become hot spots with peak rates of ~50 mm/yr. We further model the subsidence time-series with 22 years of piezometric records to estimate hydrogeological properties in the area. The modeling yields a mean consolidation coefficient of 0.56 m2/yr, a value typical for aquitards composed of > 90% fine-grain materials. The model also predicts another 0.5-1.3 m of subsidence in Ha Dong by the end of this century. Based on these results, we propose zoning for subsidence susceptibility as the basis for future groundwater management in Hanoi. From a regional perspective, Hanoi is relatively less affected by land subsidence compared to other South East Asian cities due to geotechnical factors including small consolidation coefficients, as well as social factors such as lower population density.