Shoreline evolution along Benin coast using satellite data through CASSIE Tool

Abstract Satellite imagery has been used to understand coastal dynamics. In order to better adapt to the impacts of climate change, it is imperative to continuously monitor coastal zones. To this end, automatic shoreline mapping and analysis tools such as Coastal Analyst System from Space Imagery Engine (CASSIE) are now in use. The aim of this study is to analyze the coastal dynamics along Benin coast, by assessing the rate of shoreline evolution generated by CASSIE tool basing on satellites images from 1984 to 2023, evaluating erosion trends over the entire Benin coastal zone, and determining the different hotspot along this coast. To assess the coastal features of the CASSIE tool, the method based on satellite data and the video camera system at Grand Popo was used, drawing on Sentinel 2 and Landsat data. It can be seen that shoreline generated by CASSIE are within the range of values read by the camera data. Cloudy images were rigorously eliminated. Nonetheless, shorelines detected by Sentinel2 moderately reproduce those in-situ and highlight the strong erosion trend evident during summer and mainly during July and August. In general, Benin's shoreline is marked by alternating, erosion, stability situation, accretion from Hilacondji to Cotonou . Zones of very strong erosion are recorded on beaches bordering protection structures (groynes) at the eastern part of Cotonou Harbor, which are classified as critical erosion with more than 15 m/year of erosion sites while significant accretion is obtained at western part of PAC over the period of 1984 to 2023.