Evidence of dynamics reversal in tropical estuaries, geomorphological and sedimentological consequences (Salum and Casamance Rivers, Senegal)

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.

Impacts of climate change on the Senegalese coastal zones: Examples of the Cap Vert peninsula and Saloum estuary

“…Most of the Saloum estuary is protected from the ocean by the Sangomar sand spit which breached in February 1987 due certainly to storm waves. This estuary has been characterized as an "inverse estuary" (Barusseau et al, 1985(Barusseau et al, , 1986 with high salinities of more than 80%o upstream resulting from the seawater penetration and high evaporation in this region (Debenay et al, 1994;Pages and Debenay, 1987). The region has a low density population (between 64 and 160 inhabitants per km 2 ) with around 537,000 inhabitants in 1992 representing 7.2% of the national population.…”

Caractérisation des sols de la vallée rizicole de Tamra dans l’île de Mar, Centre-Ouest du Sénégal

“…Le bassin du Sine-Saloum a connu durant le quaternaire récent des fluctuations climatiques (transgression et régression) ayant influencé les dépôts de sédiments en quantité et en qualité notamment dans les anciens golfes marins (Barusseau et al, 1985). Ainsi l'analyse granulométrique effectuée par (Marius, 1979) dans différentes îles du Saloum a révélé des sédiments essentiellement sableux (sables fins) et argileux.…”

Growth and exploitation parameters of Ilisha africana, by-catch of the experimental fishing for the study on selectivity of gill nets for Ethmalosa fimbriata, in the Saloum estuary and Joal (Senegal)

“…These sites are both located at the south of Senegal. The Saloum estuary belongs to the category of inverse estuaries (Barusseau et al, 1985;Pages and Citeau, 1990;Diouf, 1996). This estuary is no longer receiving freshwater inflow.…”