Coastal dunes as a resilient factor: a new challenge for coastal system management: exemple from Bevano River (Ravenna, Italy).

Coastal dunes are natural accumulations of sand formed by winds. Their occurrence, size and shape mainly depend on: winds strength and direction, grain size, beach amplitude and vegetation cover. Another factor that has a very strong (and negative) impact on coastal dunes is Human exploitation of the coast. Past policies of coastal bad management have brought about a very damaged system, where dunes are often stressed or even absent. This work aims at describing the function of dunes along an exploited tract of coast where dunes act as a natural defence against storms, erosion and wave attack; but they also have a very important role in defending landward areas against saltwater intrusion. The Province of Ravenna is particularly affected by subsidence that causes lowering of already depressed areas and worsens the saltwater intrusion phenomenon. Along this coast, dunes are the only elements that lay above the ground. Moreover, dunes have a great infiltration capacity (Tsoar, 2005) and they can accumulate fresh groundwater, the water table, standing above sea level, that acts as a hydrostatic control on saltwater intrusion, by contrasting the seawater density head. We evaluated the influence of dunes in minimizing saltwater intrusion by comparing different data obtained from groundwater table height and salinity.