24th Pacific Science Congress (PSC-24)

Coastal cities function as complex urban metabolic systems in which material stocks, energy flows, and environmental dynamics interact under multiple stressors. Global sea-level rise (SLR) and regional vertical land motion (VLM) jointly reshape these metabolic exchanges between the built environment and surrounding ecosystems, influencing the long-term sustainability of urban material and energy cycles. However, existing studies mainly emphasize economic losses while overlooking how SLR–VLM interactions modify the three-dimensional (3D) material exposure and carbon-related vulnerability of urban building stocks. To address this gap, we develop an improved hydrological-connectivity inundation algorithm integrating SLR, VLM, and 3D building stock data to simulate future exposure scenarios (2050 and 2100) for Tianjin, China—a representative subsiding coastal metropolis. Results indicate that by 2100 (SSP5-8.5), up to 20% of Tianjin’s land could be inundated, with building exposure volumes nearly doubling relative to 2050 and total material losses reaching 167–392 Mt, dominated by concrete (52%), implying substantial embedded carbon emissions. VLM further exacerbates inundation impacts, expanding affected land by 40–48% and exposed building volumes by 13–25%, particularly in dense subsiding zones. This study frames coastal subsidence as a metabolic disturbance in which the physical mass of cities becomes a latent carrier of risk. The integrated assessment of SLR, VLM, and 3D building stocks offers a useful perspective for understanding material vulnerability and informing more resilient and sustainable urban development in subsiding coastal regions.
 

Relative Sea-Level Rise (RSLR),Urban 3D Building Patterns,Building Exposure,Climate Risk Simulation,Coastal Adaptation Action