Inundation risk in North China’s coastal gateway amid land subsidence, sea-level rise and coastal defense initiatives

Sea-level rise causes land loss and threatens coastal communities. Although the Intergovernmental Panel on Climate Change (IPCC) reported relative sea-level projections incorporating partial vertical land motion, the remaining relative local land subsidence is overlooked. Here, we leveraged high-resolution relative local land subsidence, sea-level rise, and demographic projections to provide a refined assessment encompassing the Bohai Economic Rim, China. Our results demonstrate that, by 2100, IPCC reported relative sea-level rise alone can cause a land loss of 373–458 square kilometers in this region, while additional relative local land subsidence may amplify such loss by approximately 110%-260%. The present-day coastal defence initiatives, such as levee systems, can mitigate future flood extent by ~400 square kilometers and reduce the exposed population by ~111,000 in 2100. Moreover, adults face 10 ± 2% greater coastal flood risks. Our study demonstrates that integrating relative local land subsidence is critical for coastal risk assessment and strategic planning. By 2100, IPCC (Intergovernmental Panel on Climate Change) reported relative sea level rise may erase 373 to 458 square kilometers in the Bohai Economic Rim, with local land subsidence increasing losses by 110 to 260 percent; levees reduce flooding and population exposure, according to satellite radar, sea level rise, and demographic projections