An analysis of spatial mismatch and coordination mechanisms in river-sea systems

China's port system within the Yangtze River Economic Belt has evolved from a traditional coastal port–hinterland structure into a more interactive coastal–inland port network. Coastal ports such as Shanghai port now operate as interconnected nodes, where coordination and investment interdependence increasingly shape port relations. While existing studies generally view coastal port investment as enhancing hinterland connectivity and inland port efficiency, less attention has been paid to whether this relationship varies across geographical, economic, and institutional conditions in China's rapidly evolving river–sea intermodal logistics system. Using a DEA-based cross super-efficiency model with non-discretionary inputs and a two-way fixed effects regression, we examine the relationship between Shanghai Port's long-term investment and inland port performance along the Yangtze River Economic Belt. The results show a significant association with higher measured inland port efficiency, with pronounced heterogeneity across these distance dimensions. We further propose a cognitive bias mechanism in which misaligned strategic priorities between dominant coastal ports and inland ports lead to persistent efficiency mismatches. By integrating spatial, institutional, and behavioral dimensions, this study advances the literature on intermodal port integration and provides insights for developing more adaptive and resilient port governance frameworks.