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

The aim of this study is to improve regional coastal flood risk assessments by incorporating high-resolution measurements of land subsidence, updated coastal sea-level data, and a physics-based modelling approach to evaluate future coastal flood exposure in China's Greater Bay Area under climate change and sea-level rise. The study specifically addresses limitations in previous regional-scale flood risk assessments, which often overlook spatial variations in land subsidence and rely on simplified modelling methods. Coastal flood risk is intensifying worldwide due to the combined effects of relative sea -level rise s and the climate -driven amplification of extreme events, such as storm surge

The results show that by 2050, the combined effects of subsidence and sea-level rise will expose an additional ~222 km2 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.