Factors controlling land subsidence in the Southern Hau River Region, Vietnam

The Vietnam's Mekong Delta (VMD) is known to be sinking below the sea due to climate change induced seawater level rise on one hand and land subsidence on the other hand. This phenomenon has deleterious ramifications for sustainable socio-economic advancement, manifesting in infrastructure degradation, recurrent inundation, intrusion of saline water, and reduction of habitable and cultivable areas within the region. Notably, in locales such as the Southern Hau River Region (SHRR), land subsidence rates as high as −10 cm/year have been documented, primarily associated with excessive groundwater extraction. Previous investigations have corroborated this relationship through the congruence between groundwater drawdown cones and areas of subsidence detected via InSAR (Interferometric Synthetic Aperture Radar) or through coupled Terzaghi consolidation theory-groundwater flow numerical modeling. This study extends the understanding of subsidence drivers in the SHRR beyond the groundwater level declining, encompassing tectonic activity, geological - lithological features, and landuse. Utilizing geostatistical analyses based on individual InSAR monitoring points, the study evaluates the respective contributions of these factors to land subsidence in the SHRR. Findings indicate that auto-compaction of young sediments, structural loading, and sediment compaction due to induced groundwater level decline are the principal factors precipitating land subsidence in the SHRR.