Management strategies for coastal erosion problems in west Africa: Analysis, issues, and constraints drawn from the examples of Senegal and Benin

In West Africa, coastal erosion remains a problem for the socio-economic development of the coastal zone. Case studies in Senegal and Benin indicate a strong intensification of coastal erosion, in relation to human influence, as shown by the analysis of shoreline change rates from satellite data. The “Langue de Barbarie,” a sand spit bounding the mouth of the Senegal River delta in the Saint-Louis Region, Senegal, is relatively densely inhabited and developed. The spit was artificially breached in 2003 to alleviate potential river flooding that threatened the historical city of Saint-Louis. The analysis covers two periods: the pre-breach period (1984-2003) characterized by sectors alternating between erosion and accretion, and the post-breach period (2003-2016) indicating a generalization of the erosion process, with a noteworthy average rate of −3.72 m/yr affecting the entire spit, strongly destabilized by the artificial breach. In Benin, shoreline evolution is equally affected by human interventions. Following the construction of the Nangbéto Dam on the Mono River, the “Bouche du Roi,” outlet of this river, has been characterized by marked instability, with an eastward migration exceeding 700 m/yr. Other human alterations of the coastal system include the installment of major seaports and groins that have resulted in some erosion downdrift near Cotonou. These examples highlight the limits of governance regarding the coast in West Africa, including adaptation strategies developed at regional, national and local levels, which often produce more setbacks than solutions.