TUMBLING EXPERIMENT FOR THE ESTIMATION OF ABRASION AND MASS LOSS OF COASTAL SEDIMENTS FROM AN ARTIFICIAL COARSE-CLASTIC BEACH

Abstract

In order to assess the accretive or erosive pattern of a stretch of coast, it is essential to estimate its sediment budget, i.e. the quantification of all sources and sinks of sediments. The sediment budget is the basis of a reliable coastal management plan (Ruol et al., 2018). In fact, coastal erosion is usually the result of a negative balance of factors, both natural and anthropogenic, that operate on different scales, none of which may be considered the single cause. Recently, a massive abrasion rate of coarse-clastic sediments was documented in artificial nourished beaches. The mechanism is associated with both mild wave conditions and extreme stormy events, which could also induce chippings. This phenomenon could decrease the durability of nourishments (Bertoni et al., 2012 and 2016) and is usually not considered in the sediment balance. The mass loss due to abrasion can lead to errors in the analysis of erosive and accretive patterns after the nourishment and consequently to erroneous coastal management strategies. Moreover, the sediment grain size in a given beach (naturally present or selected for nourishments) is strictly related to the typical wave energy. The abrasion mechanism and the possible pebble chipping change the sediment grain size, which could become unstable and not adequate for the local wave climate. Based on the large cost of nourishments, which also require strong monitoring in the subsequent years, it is crucial to understand the abrasion and mass loss rates of the filling sediments to extend the life of artificial beaches as long as possible.