Le rechargement de la plage de Sainte Anne du Portzic (Brest-Finistère) : quand la recherche fondamentale se met au service d'une gestion cohérente du littoral

The beach of Sainte Anne du Portzic used to be the sole sandy beach in the vicinity of Brest. During the second half of XXth century the gradual disappearance of sand led to a decline in attendance of this once highly praised beach. This paper presents the methodology of the feasibility study of beach replenishment. The diachronic analysis of oblique photographies and the tracing of the history of the set up of structures enabled to determine the origin of sand loss on the upper part of the beach. It is the result of the edification of man made structures that increased the reflexivity of the upper beach and of the construction of a jetty that has modified local hydrodynamism. DGPS field measurements, during an entire year, show that presently sedimentary movments are limited and never occur toward the upper beach. Granulometric analysis demonstrates that the sand has been relocated at the base of the beach and is likely to be used for replenishment. This operation will occur only once some of the structures responsible for the changes in the hydrodynamics of the beach will have been modified.