Investigation of Long-Term and Large-Scale Shoreline Evolution in West Africa Based on Optical Satellite Data

Monitoring and understanding the status of the shoreline in West Africa are significantly important for further decision making toward sustainable coastal management. This study aims to investigate the shoreline status in four countries (Ghana, Togo, Benin, and Nigeria) of West Africa by using optical satellite data obtained by Landsat and Sentinel missions over the past 35 years. Shoreline positions at 123 shore-normal transects on each satellite image were estimated by using CoastSat. It is found that 68% of the shorelines at the transects retreated in the last 35 years. Both the maximum retreat and the maximum advanced extent were larger than 300 m. The significant shoreline change was found mostly around ports which prevented the longshore sand transport. The effect of beach protection measures such as groins was found to be limited. Severe erosion was accelerated at downdrift areas. These results highlight the importance of such international large-scale shoreline monitoring presented in this study. In addition, regional cooperation is urgently needed for sustainable development of this area.