Abstarct: Understanding the hydrodynamic phenomena and their effects on marine and coastal processes is important for optimal port utilization. One of the most important marine phenomena is sedimentation and erosion in and around ports. The construction of harbors in coasts disrupts the coastal flow and as the upstream coast progresses, the inception of the sediment bypass in front of the harbor causes sedimentation problems in the port. One of the reasons for this concern is the incompatibility of breakwater geometry. Dredging sediment accumulated in harbors adds heavy expenses to harbors each year. In this research ، first, the methods of adapting harbors with natural sediment bypass and geometrical modification of harbors breakwater to reduce sedimentation are investigated. Then, two-dimensional numerical modeling was performed in Mike21 software to investigate the hydrodynamic status and sedimentary problems of Nowshahr Port, one of the major northern ports facing the problem of sedimentation in the access channel and harbor entrance. baxsed on the results and identifying the factors influencing the sedimentation of this harbor, four scenarios were evaluated and compared to reduce these difficulties. Finally, scenario number 4 was selected as the optimal design by reducing the dredging volume by approximately 90 percent compared to Nowshahr harbor dredging condition in recent years.