Determining the relative contributions of inland and marine sediment sources is essential for accurately predicting and managing sedimentation in harbors. The Savannah River navigation channel is characterized by strong tidal currents, which move water and sediments in and out of the system with the tides. A hydrodynamic-wave model was developed to accurately reproduce water surface elevations and tides, which were then used to compute longshore sediment transport (LST) at locations south of the outer Savannah River channel near Tybee Island. Southward transport rates were 485,864 m³/year at East Tybee Island and 728,080 m³/year at Southeast Tybee Island. In contrast, North Tybee Island exhibited a northward transport rate of 144,601 m³/year, confirming a previously reported local reversal. The computed rates align with previous LST estimates but are significantly lower than dredging records. This discrepancy suggests reduced sediment availability south of the channel, likely due to sediment trapping in the channel.