Human-induced subsidence exceeds sea-level rise in driving future coastal flood exposure in China’s Greater Bay Area

Effective coastal flood risk assessments are essential for adapting to climate change-driven sea-level rise and other coastal hazards. However, regional-scale assessments often remain limited by the neglect of spatially variable land subsidence and oversimplified modelling approaches. Here we address these gaps by integrating high-resolution land subsidence observations with the latest coastal sea level altimetry and applying a physics-based model to assess future coastal flood exposure in the Greater Bay Area of China. Our results show that by 2050, the combined effects of subsidence and sea-level rise will expose an additional ~222 km 2 of land and 228,900 people to coastal flooding. Human-induced subsidence is the dominant driver of this increase. Maintaining future flood exposure at present-day levels would require raising coastal land elevation by 0.45 m on average, 66.7% of which is attributable to subsidence, highlighting the need to explicitly account for spatially variable subsidence in regional coastal flood risk assessments.