CALAFELL-VENDRELL BEACH NOURISHMENT EVOLUTION:IS THE “COASTAL BOX” CLOSED OR OPEN?

摘要

Beach nourishment has been considered as one of the most powerful methods torncontrol beach erosion problems. The evolution of beach fill depends on the stability of thernsediment budged in a stretch of coast. It can be defined a “coastal box” and analyze fillrnequilibrium in it. If sediment fluxes run parallel to the coast, the fill volume change but the sandrnremains inside the system. If the sand goes out of the “box” in the cross-section direction, it isrnlost from the system.rnIn this paper a case study is showed and the analysis of its stability is made. Longshorerntransport, closure depth, and erosion and accretion areas are the key in the determination ofrnnourishment effectiveness. Two marinas interfered the beach stability and affect the sedimentrnbudged. After nourishment works a monitoring program was carried out and the analysis of topobathymetricrnsurveys, grain size distribution samples, and wave data were obtained. Also somernnumerical models were used in order to understand beach behavior. For the analyzed case thesernprocesses initially induced the formation of a tombolo to be lately reflected in a bottomrnmodification seaward of the two marinas where the deposition of part of the material beingrntransported along the coast produced a change in the theoretical seaward limit of the littoral cell.rnAfter all of this it can be assumed that the “box” is closed in cross-shore direction and thernsediment fluxes run in longshore direction.