Tam Quan fishing port, one of Binh Dinh province’s three major fishing ports, serves approximately 1400 local and neighboring fishing vessels. However, since 2010, the Tam Quan inlet has faced escalating sedimentation, with an annual accumulation of 50,000 to 150,000 cubic meters of sediment. Despite the construction of an 850-m-long jetty on the southern coast and ongoing dredging efforts, sedimentation remains a persistent challenge. The dredging and relocation of dredged materials from the Tam Quan inlet have inadvertently disrupted the sediment balance, leading to instability and severe beach erosion along the southern coast of Tam Quan. To address these issues, this study employs mathematical modeling, calibrated and validated using updated measurement data collected during the summer of May 2022 and the winter of November 2022. The hydrodynamic characteristics and sediment transport dynamics were simulated to identify the main causes of sedimentation at the Tam Quan inlet and erosion along the southern coast. The simulation results clearly demonstrate a strong correlation between sedimentation at the river mouth and beach erosion along the southern coast, providing a solid foundation for developing future solutions.