Morphological and sedimentological changes in the Senegal River estuary after the constuction of the Diama dam

Abstract

The aim of this paper is to study the behaviour of a complex and unstable coastal system (the Senegal River delta) since the construction of the Diama dam. The Senegal River mouth is located on a sandy microtidal coast. The equilibrium of the coastline (the so-called “Langue de Barbarie” sand spit in particular) and the inner part of the river mouth is highly dependent on the longshore drift and the transported sandy material. The role of the Diama dam could therefore be very important according to the seasonal rainfall. For example, between 1986, after the Diama dam began to function, and 1990, the Senegal River mouth moved southwards by more than 2.8 km and is now located in its southernmost position. As a whole, the high accretion has helped strenghen the maritime segment of the “Langue de Barbarie” by a decreasing of the fluvial water discharge and the Senegal River mouth will be maintained for a while at the southern part of the delta. Field measurements, including topography profiles, sounding transects and sedimentological analysis, Spot-imagery processing and comparisons of recent topographical maps have been used to evaluate the functioning and evolution of the Senegal distributary and coastal zone.