Effective coastal exposure assessments are crucial for adaptively managing threats from sea-level rise (SLR). Despite recent advances, global and regional assessments are constrained by omitting critical factors such as land-use change, failing to disaggregate potential impacts by land uses and oversimplifying land subsidence. Here we address these gaps by developing context-specific scenarios to 2100 based on a comprehensive analysis of Chinese coastal development policies. We integrate high-resolution simulations of population and land-system changes with inundation exposure assessments that incorporate SLR, land subsidence, tides and storm surges, offering a more nuanced understanding of coastal risks. Across our plausible set of downscaled scenarios of shared socioeconomic and representative concentration pathways, policy decisions have a bigger effect on what is exposed to coastal flooding until 2100 than does the magnitude of SLR. Hence, coastal policy decisions largely influence coastal risk and adaptation needs to 2100, demonstrating the necessity of appropriate policy design to manage coastal risks.