Evidence of dynamics reversal in tropical estuaries, geomorphological and sedimentological consequences (Salum and Casamance Rivers, Senegal) |
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Authors: | J. P. BARUSSEAU&dagger ,E. H. S. DIOP&Dagger ,J. L. SAOS§ |
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Affiliation: | Department of Geology, Dakar University, Dakar-Fann, Senegal;Department of Geography, Dakar University, Dakar-Fann, Senegal;O.R.S.T.O.M., Dakar, Senegal |
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Abstract: | South Dakar Senegambian estuaries are subject to an unusual hydrodynamical regime caused by weak or absent run-off. In the Salum delta, each distributary lacks fresh water during most of the year. Only the tidal flows are responsible for geomorphological and sedimentological effects. The current distribution shows a net discharge upstream due to the extensive evaporation and evapotranspiration in mangrove swamps and tidal flats. Consequently the salinity is always higher towards the river than near the sea. A high salinity bottom layer suggests the occurrence of a supersaline wedge of reverse sense to the salt wedge of a normal estuary. Such an inverse pattern is similarly displayed by sedimentological features (double upstream turned spits) and by the external location of the turbidity maximum. A coherent reverse estuary model is suggested from our field observations. |
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