Monitoring the spatial and temporal variability of the Sangomar spit (Senegal)

Résumé

About 70% of the world’s sandy coasts experience coastal erosion issues materialized by varying rates of shoreline retreats. The Sangomar spit, a sandy cordon located on the south coast of the senegalese coastline, is no exception to this phenomenon. After four natural cuts in 1860, 1928, 1952 and 1954, it was again broken in february 1987. The analysis carried out using available satellite data consisted of retracing the dynamics of the coast along the shoreline of the spit and then following the kinematics of the mouth after its opening.The results obtained show an evolution of the spit dominated by accretion phenomena before its breaking. However, after its beaking in 1987, the movements became mainly erosive, leading to a progressive widening of the breach. The consequences of these two movements are significant. Indeed, they caused, for example, a remarkable sediment displacement at the origin of the development of a new spit at Dionewar. In addition, topographic methods allowed to highlight relatively narrow beaches with a certain variability in morphological characteristics depending on the wave regime. The average width is 40 m and the average slope is 7,63 %. The dominant shape of the profiles are more variables one sector to another and from one period to another.