Dynamic vertical land motion driven by climate and humans in the metropolitan Taipei Basin

This study investigates basin-wide vertical ground motion in metropolitan Taipei between 2009-2023 using geodetic data. Despite seasonal variations of ∼1 cm, we observed two major subsidence episodes: a 2-cm subsidence during 2009-2012 followed by complete recovery within a year, and a 2.5-cm subsidence during 2018-2022 with subsequent 2-cm rebound. Analysis of rainfall data, groundwater levels, and construction activities reveals that these deformation patterns correlate with both climate factors (drought and rainfall) and human activities (major construction projects). On the first order, the basin-wide deformation are controlled by climate, subsiding in dry years and uplift in wet years. However, areas undergoing intensive redevelopment exhibited 0.5-1 cm greater net subsidence than surrounding regions, indicating irreversible deformation in these zones due to the combined effects of construction-related groundwater extraction, increased surface loading from new buildings, and soil compaction during development activities. These findings highlight the complex interplay between natural and anthropogenic factors in urban ground deformation and emphasize the need for integrated water-management strategies in the context of climate change. • Despite tight groundwater regulation, most of the Taipei Basin subsides rapidly during droughts and rises rapidly during wet years. • Areas of intensive development subsided during drought and wet-interval years, suggesting some activities cause irreversible deformation. • Net subsidence may expand throughout much of the Taipei Basin if drought severity and/or duration increase as climate change progresses. Plain Language Summary : Beginning in the 1950s, the densely populated Taipei Basin experienced land subsidence following extensive groundwater extraction. To prevent further subsidence, Taiwan instituted strong groundwater regulation beginning in 1971, including a complete ban on groundwater extraction. Despite these regulations, the basin sank 2 cm within 3 years starting in summer 2009, but recovered fully by summer 2013. The basin sank again (by 3 cm) between summer 2018 and early 2022 and then quickly uplifted by 2 cm within 6 months. It is unclear if the ground will recover to pre-2018 levels. Correlation with the timing of major urban projects and rainfall data indicates that both climate and human activities have contributed to the sinking and rising of the basin. Climate change is the main reason for basin wide subsidence and uplift. However, a redevelopment zone in the west part of the basin showed greater net subsidence than the rest of the basin, suggesting development projects cause irreversible subsidence. Ground subsidence is happening in many cities around the world for similar reasons and we call for comprehensive water management strategies in the era of anthropogenic climate change.