Coupled ground subsidence and rapid urbanization of the Red River delta region and the city of Hanoi, Vietnam, revealed through a Multi-Track InSAR analysis

The region of the Red River Delta represents one of the most crucial economic zones of Vietnam, and its capital, the city of Hanoi, is in the heart of the delta. To satisfy the water demand for agricultural irrigation, urbanization, and industrialization, over-pumping groundwater-induced-ground subsidence has long hindered the region’s sustainable development. Existing studies do not systematically assess land subsidence with two-dimensional analysis in the RRD mega-city region. In this work, a comprehensive analysis relying on the exploitation of the interferometric SAR technologies and the use of multi-track SAR datasets acquired from the European Copernicus Sentinel-1 and TerraSAR-X has been carried out to generate and interpret the 2017–2024 dynamics of the RRD terrain deformations, by generating 2-D maps, along the vertical and horizontal directions, and ground deformation time series. As a result, the megacities Hanoi, Hai Duong, and Nam Dinh of the delta are found to be affected by significant subsidence. Specifically, we found that substantial subsidence occurred in the urban-suburban fringe of Hanoi (four districts: Ha Dong, Hoai Duc, Thanh Tri, and Dan Phuong). Experimental results confirm that the subsidence dominated the ground deformations, whereas the horizontal displacements of the terrain (i.e., along East-West) are almost negligible. Our study also comprehensively analyses the relationships between population, land-cover changes, the distribution of built-up areas, the role of over-pumping groundwater, geological setting, and ground subsidence, revealing that geological setting and groundwater pumping are dominant factors of the observed ground subsidence bowls.