Small rivers play a significant role in the morphological processes of sandy beaches, as they interact with the seabed and wave-driven currents. This study investigates the influence of the Ropotamo River (Northwestern Black Sea) on the shoreface zone under various scenarios. A combination of What-If Scenarios (WIS) and Nature-based Solutions (NbS) approaches was applied using the XBeach model in 200 numerical experiments, integrating different wave and discharge conditions. WIS simulated extreme wave climates and riverine discharges, while NbS incorporated seagrass meadows to mitigate erosion. The results highlight that river discharge affects all scenarios, altering wave action, sediment transport, and recirculation patterns. Seagrass meadows proved effective in reducing erosion across diverse conditions, underscoring their potential for coastal restoration. These findings emphasize the Ropotamo River’s discharge as a critical factor in shoreface dynamics, with implications for operational systems and the integration of NbS strategies. The study reinforces the importance of considering small rivers in coastal management to enhance resilience against erosion and habitat loss.