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Évolution et fonctionnement hydro-sédimentaire de la lagune de la Somone, Petite Côte, Sénégal.

Abstract : Located at the Petite Côte of Senegal, Somone is a small coastal river that flows into the Atlantic Ocean by a microtidal lagoonal-estuarine ecosystem. Today, the contribution of the watershed is absent due to a combination of several factors including the dam of Bandia. The only freshwater inputs are from precipitation and groundwater. Somone is a lagoonal-estuarine system characterized by an inverse hydrological functioning where marine influences predominate. Mangrove, dominated by Rhizophora, is the main characteristic unit of this coastal system. The diachronic evolution of 60 years shows a significant change for all the morphological units of the ecosystem. The mobility of the sandy spit, which caused the closures of the mouth in 1967-1969 and in 1987, is related to meteorological variations. The regressive surface of mangroves between 1954 and 1989 is the result of the combined effect of these closures of the mouth, drought and traditional uses of mangroves. The restoration of the mangrove is mainly due to reforestation policies administered in the 2000s. The annual and seasonal trend shows that the internal reworking is the main hydro-sedimentary processes. Sedimentation rate of the mud flats is 2 to 3 mm/year. The dynamics of the sandy spit of the Somone plays an important role in the development and quality of internal units, the mangroves in particular. The permanent opening of the mouth allows a twice-daily renewal of water in the lagoon, which is essential for regulating the high salt content. The low content of sediment in total organic carbon, reflect the low organic matter production of the mangrove because it is a young and stunted mangrove. Diagenetic processes are anaerobic and mostly in the top 10 cm of the sediment, on the recent deposit. The contribution of young mangroves, like Somone, in the carbon storage process, is low. The lagoonal-estuarine ecosystem of the Somone is fragile and highly reactive and his evolution is fast and linked to the cumulative effects of natural and anthropogenic factors.
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https://tel.archives-ouvertes.fr/tel-00680519
Contributor : Issa Sakho <>
Submitted on : Thursday, September 26, 2013 - 3:45:32 PM
Last modification on : Friday, October 23, 2020 - 4:38:10 PM

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  • HAL Id : tel-00680519, version 1

Citation

I. Sakho. Évolution et fonctionnement hydro-sédimentaire de la lagune de la Somone, Petite Côte, Sénégal.. Sciences de l'environnement. Université de Rouen; Université Cheikh Anta Diop de Dakar, Sénégal, 2011. Français. ⟨tel-00680519⟩

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