Satellite, drone and video camera multi-platform monitoring of coastal erosion at an engineered pocket beach: A showcase for coastal management at Elmina Bay, Ghana (West Africa)

Regular monitoring of coastal areas is a prerequisite to evade any imminent erosive disaster. However, data-driven decisions become more uncertain when a monitoring platform is unable to capture events of a certain frequency. Erosion along Ghana's coastline is endemic as in most of the Gulf of Guinea countries in West Africa. The current challenge is how to document and understand the dimensions of erosion despite limited human and logistical capacity. In the present study, shoreline change was assessed by an intensive multi-platform data collection strategy deployed for a year at Elmina Bay, Ghana through the use of drones, a shore-based camera, Sentinel satellite images and a dumpy level. The potential causes and areas of erosion at Elmina were clearly identified at a very fine scale by our sediment budget calculations. While a section of the beach in front of the Elmina Castle was adequately protected by the presence of jetties , downdrift of the larger unprotected portion of the beach was out of balance with high erosion rates. Furthermore, the results revealed that frequent, local video cameras and drones are more effective for operational monitoring of shoreline changes at all time scales. Satellite imagery is also a potential alternative tool, but its low temporal resolution, compared with video cameras, makes it unsuitable for detecting daily or event-based beach changes, and is of low accuracy for practitioners and management decisions. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

Regular monitoring of coastal areas is crucial for mitigating erosive disasters. The erosion along Ghana's coastline, like other countries in the Gulf of Guinea, is a persistent issue. This study used multiple data collection methods, including drones, cameras, satellite images, and a dumpy level, to assess shoreline changes in Elmina Bay, Ghana. The results identified the causes and areas of erosion at a fine scale and highlighted the effectiveness of local video cameras and drones for monitoring shoreline changes. Satellite imagery, although a potential alternative, has limitations in temporal resolution for detecting daily or event-based beach changes.