Extreme erosion of a dune crest within a short timespan (january – september 2016): the recent case in the Migliarino – San Rossore – Massaciuccoli Regional Park (Tuscany,Italy)

Beach erosion is a process that in the last decades is affecting several coastal areas around the world. Unfortunately the Tuscany coast makes no exception. The factors responsible of this phenomenon are different: some are natural, some other are related to human activities. Usually the latter determine drastic hastening of ongoing processes, mainly because they act over temporal scales much smaller than those typical of the natural factors. In this paper, multiple topographic surveys were carried out along a 5 km long sector of coast located within the boundaries of the Migliarino – San Rossore – Massaciuccoli Regional Park in order to evaluate the evolution state of the area within a 9-months timespan (January 2016 – September 2016). The results emphasize the importance to increase the knowledge about the morphodynamics processes acting on this area based on the resulting retreat that was observed analyzing the data: in just 4 months the crest of a 9 m high dune retreated of about 6 m, which resulted in a volume loss of about 80 m3/m along the selected transect. This worrying outcome implies the need to manage this sector of coast applying a rather different approach relative to those used thus far. It is paramount to consider each sector of coast as a whole and not separately, that is in accordance with the physiographic unit rather than territorial and administrative limits. In addition, this new approach must also take care of the coastal environment in the direction orthogonal to the coastline, adding into the equation rivers and catchment areas, which are the main source of sediments feeding the beaches.