Monitoring shallow coastal bathymetry and sediment dynamics with modern fishfinder bathymetry data: A case study in the Ardeşen fishing harbor (Rize, Türkiye).

Monitoring coastal sediment dynamics and morphological changes is important for sustainable coastal management. This study aimed to examine sediment dynamics and bathymetric changes in the Ardeşen Fishing Harbor using a low-cost, sonar-based modern fishfinder system. A comparison of bathymetric data from 2007 and 2024 using Geographic Information System (GIS) tools revealed a sediment accumulation of 602,373 m³. This accumulation is the result of engineering interventions, including land reclamation activities carried out as part of the Black Sea Coastal Highway Project and the redirection of the Dolona Stream. As a result of sediment deposition, the shoreline migrated seaward by 85 meters, creating a new sediment deposit area of 5,100 m². This accumulation progressing toward the harbor entrance poses a significant threat of increasing shoaling and a potential reduction in harbor functionality. The findings draw attention to the long-term impacts of engineering interventions on coastal morphology and demonstrate that low-cost, sonar-based bathymetric monitoring methods provide an effective tool for the regular and efficient monitoring of coastal processes, thereby contributing to sustainable coastal management.