Abstract
In this paper, coarse sediment displacement has been assessed on an artificial pebble beach located at Marina di Pisa (Italy). Four topographic surveys have enabled volume reckoning and comparisons between the different stages of beach evolution. Data from the backshore to the foreshore were collected with an RTK-GPS instrument, while data from the shoreface were taken with echo-sounder equipment, and the outcomes processed with ArcGIS software. The research was performed in a two-years span of time. The surveys were carried out just before the stormy season, which typically begins in mid-Autumn, and after a series of intense high-energy events that led to a profound modification of the beach profile. The results showed both longshore and cross-shore sediment displacement; in particular, a volumetric increase of the proximal part of the backshore and a volumetric decrease of the submerged portion of the beach. Besides, a general volume decrease of the entire beach system has been acknowledged, most notably after the second year, leading to the supposition that processes such as sand fluidization, sediment weight and permeation have a major role in the adjustments an artificial coarse-grained beach is subjected to. As well as confirming the tendency of coarse beaches to accrete after significant high-energy events, these results might be useful to better understand the physical processes governing gravel beaches and, to a further extent, to improve and optimize protection schemes, such as coarse replenishments, which are increasingly used as a form of defence structure. In addition, they could provide insights about the depositional processes occurring on coarse-grained coastal environments, which might improve the definition of ancient gravel beaches in the geological record.
Keywords: Volume displacement, Artificial pebble beach, Coarse sediment transport, Coastal erosion, Marina di Pisa