Assessing the efficacy of nourishment of a Mediterranean beach using bimodal fluvial sediments and a specific placement design

Abstract

Several studies have highlighted the difficulties inherent to the use of bimodal fluvial sediments in beach nourishment and the resulting unpredictable behaviour of the beach profile. In this paper, we monitored the temporal evolution of a nourishment project carried out on a northwestern Mediterranean beach and using fluvial mixed sand and gravel nourishment material. The main aim of the study was to examine the morpho-sedimentary evolution of the beach from the injection of the nourishment material to the attainment of a targeted equilibrium profile. The monitoring activity was conducted coupling multiple topo-bathymetric surveys and sediment sampling. The data show that the targeted equilibrium profile was attained less than 2 years after the nourishment, and, since that period, the shoreline has shown minimal mobility. Our results show that the positioning of the nourishment material is as important as the correct choice of grain size to attain rapid and successful nourishment of a beach. Further applications of this methodology in other coastal settings and/or with different nourishment sediments (e.g. medium or fine sands) are presently being considered. If confirmed at a broader scale, this nourishment design, employing bimodal fluvial sediments, should significantly contribute to the mitigation of beach erosion.