1. Regional sustainability occupies a central position in contemporary policy and academic discourse, as regions worldwide seek to define strategic priorities that secure resource availability whil...

Global climate change intensifies hydrological extremes, challenging inhabited floodplain landscapes where environmental regulation, socio-economic decline, and institutional ambiguity co-produce persistent development traps. Research on sandbar islands – dynamic, inhabited landforms in large river systems – has largely overlooked the integration of social and economic dimensions. Using Tianxingzhou, a mid-Yangtze sandbar, as a critical case, this study integrates socio-economic conditions, natural resource and environmental characteristics, infrastructure status, governmental planning and regulatory guidance, and field observations with iterative SWOT analysis. Findings reveal a self-reinforcing development trap driven by four interacting dimensions: deteriorating socio-economic conditions (aging, outmigration, economic monostructure); vulnerable natural assets (fertile but flood-exposed); stagnant infrastructure (minimal public services); and policy stasis (no detailed spatial planning document update since 2013). These dimensions lock the island into a state where neither abandonment nor revitalization can proceed smoothly. A three-pillar sustainability framework (environmental–social–economic) is proposed, translating SWOT-derived strategies into testable heuristics. The framework provides a realistic pathway from lock-in to adaptive coexistence, with transferable principles for climate-vulnerable riverine and deltaic settlements worldwide. The findings offer a paradigm for balancing environmental conservation, socio-cultural engagement, and economic sustainability in ecologically sensitive island environments.