Erosion of a sandy coast: continuous follow-up of the coastal groynes of protection in Boumerdes (Algeria)

The "waterfront" of Boumerdes saw a development in 2005 which consisted of the construction from west to east of two groynes perpendicular to the coast and a shaped spike of "T" further east. These groynes of 50 m in length are constructed of concrete in the middle of the building and are protected by rockfill blocks of metamorphic rocks type. Our aim is to control the work and make a complete sedimentological study, to determine the different sources of sediment supply, to follow their distribution at the beach and finally to know the particle trapping zones along the coastal geomorphological entity between Boumerdes stream and Corso stream before and after the construction of these groynes. We have determined fattening areas or depletion sand (erosion) along the beach which is followed since 1986. We also used heavy minerals as natural tracers to determine the transit directions of sediment supply reaching the study area and their deposition. This study will draw up a report on the functioning of the groynes and make a correction in some areas with high risk of erosion after the construction of the groynes.