Morphological evolution of the lagoon system at the mouth of the EBOUNDJA river (Kribi Cameroon)

The Eboundja lagoon, located at the mouth of the river that bears its name, is a recognized natural heritage as well as an essential stake for local fisheries. Its morphological evolution is an important issue especially in the current context of climatic and environmental change. The analysis of the topographic and hydrodynamic data of the lagoon system allowed to better understand the processes governing its evolution on a seasonal scale. Natural forcing and river input appear to be the main factors in the evolution of this system. During the dry season, the system shows a tendency to slowly fill due to the accumulation of sediments forming small sandy bars measuring barely 10 cm high in early January. These accumulations develop rapidly during the first part of the rainy season and reach about 25 cm in August, thus lengthening the barrier beach towards the south under the influence of the littoral drift current and wave action. These bars are thus transformed into a new barrier beach in front of the old shoreline tending to fill in the lagoon. The volumes of sediment removed and deposited in two days are respectively 10.77 m3 and 7.75 m3. The sediment dynamics are generally in the middle and bottom of the intertidal zone. The average tidal range is 0.48 m at sea and 0.24 m in the lagoon; and the wave range is 0.125 m at sea and 3.10−3 m in the lagoon.