Dramé, Awa Bousso; Mercier, Denis; (2021) Dynamique des estuaires transfrontaliers du Sénégal et du Mono (Bénin): entre aléas météomarins, vulnérabilités et résilience des communautés littorales. In: Sané, Tidiane and Diéye, El Hadji Balla and Dia, Amadou Hamath and Descroix, Luc and Sow, Bamol Ali and Diédhiou, Paul and Diakhaté, Mouhamadou Mawloud and Ndour, Ngor, (eds.) Vulnérabilité des sociétés et des milieux côtiers et estuariens d'Afrique de l'Ouest. (pp. pp. 191-226). L’HARMATTAN-SÉNÉGAL: Dakar, Senegal.

Text Drame et Mercier 2019.pdf - Published Version Access restricted to UCL open access staff until 11 December 2025. Download (12MB)

Abstract

Climate change is significantly impacting coastal areas, and with a sea-level rise projected between 0.26 and 0.77m by 2100 (IPCC, 2018), marginal and low-lying coastal regions will be vulnerable to flooding and coastal erosion. In many coastal systems, the impacts of climate change can be exacerbated by the decisions and activities of anthropogenic development. Several cross-border rivers, such as the Senegal (Senegal-Mauritania) and Mono (Benin-Togo) rivers, are the source of conflict in coastal management due to a combination of dynamic coastal morphologies and geopolitical issues. In both these examples, coastal sandspits that frame the inlets of these river systems, experience geomorphic and hydro-sedimentary dynamics that have significant implications for trans-border relations and management. On the Senegalese side, the 2003 breaching of the Langue de Barbarie was anthropogenic in origin, similar to the Benin-Togolese one of Aneho-Grand-Popo, which is annually breached during the rainy season, and then naturally infills. Both regions are also impacted by coastal developments. Through a geomorphological approach and GIS-based analysis the Senegal inlets, sandspit morphodynamics will be examined to map flooding and erosion areas and establish the extent to which human interventions are influencing coastal change. In particular, the role of anthropogenic development and land-use change on flood risk will be considered. A bibliographic review will examine the same phenomenon for the Mono inlet to show how high exposures to coastal erosion and sea-flooding can reveal sensitive zones in cross-borders areas. The results demonstrate how the Langue de Barbarie breach measuring 4m-width in October 2003, extended to 2.25 km in 2010 and reached 5.23 km in 2018. The morphologic change of the Langue de Barbarie sandspit also resulted in two opposite geomorphologic dynamics for the northern and southern sandspits. At the same time, the sea-wall that was developed within the sandpit (Goxxu Mbacc and Guet Ndar) in a bid to protect the communities from recurrent sea-flooding will increase the erosion rates which should get steeper with Ndiago and SaintLouis harbours. Moreover, at 1.75m (flooding alert level), Saint-Louis island and the Langue de Barbarie are almost entirely flooded excepting several peripheral districts. On the Beninese side, coastal strategies are based on breaching that the longshore drift inputs fill despite rates around 200m to 700m making the sandspit migrate towards the east. The rising exposure to coastal flooding (more than 40%) of the Mono estuary pinpoints the barrier role played by the sandspit in low-laying estuaries. This paper also demonstrates how non-concerted developments in both estuaries, all outline a grim picture of how anthropogenic footprints amplify the impacts of flooding and erosion in the comple

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