Spatio-economic valuation of sand in the context of shoreline (in)stability in the Senegal estuary (West Africa), integrating DeltaDTM and LiDAR technology

Awa Bousso DRAMÉ 

Coastal erosion is an increasing challenge in coastal management, resulting from complex interactions between geomorphological features, marine forcing, and anthropogenic interventions. The growing influence of human development and intervention on estuaries and coastal area evolution has led to a global sediment crisis, particularly in tropical or low-lying deltas (for example, Niger, Senegal, Nile, and Mekong), in contrast to the emerging international sand market. Paradoxically, the economic valuation of sand within the context of ecosystem services is limited, despite the global impact of coastal erosion, particularly on the West African coast. Among these, the transboundary Senegal estuary coast has been experiencing erosional trends coupled with coastal engineering developments in Saint-Louis (Senegal) and along the Ndiago Port (Mauritania) over the past 10 years. Using high-resolution elevation datasets (DeltaDTM and LiDAR) and imagery (Landsat), this study examines sand volumes lost/gained between 2013 and 2023 along the Senegal-Mauritania coast and assesses the economic value of sand as sediment reservoirs/stocks and as an ecosystem regulator (sand transport/redistribution). Results indicate that the Senegal-Mauritania coast accumulated a net sand volume of 1.515 x 106 m³, equivalent to 10,527,000 USD in the market and 5,150,500 USD in production costs between 2013 and 2023. Coastal engineering infrastructure in Ndiago Port (Mauritania) and along the Goxxu-Mbacc-Ndar Toute also significantly impacted sand trapping, causing downdrift erosion. Findings also contribute to the unexplored field of coastal ecosystem services economic valuation in West Africa, offering new insights into the intrinsic value of sand as a reservoir and a vital ecosystem regulator.