Analisi dell'influenza del tipo di suolo sull'erosione dei margini di barena

The stability of estuarine and lagoon environments in the face of changes in the environmental forcing is quite an important issue in many systems worldwide, for the progressive disappearance of typical morphological features of these systems. Several factors contribute to undermine possible equilibrium conditions: subsidence, the decrease in sediment delivery to these systems, climate changes such as sea level rise and the increase in the frequency and magnitude of storms. Salt marshes are typical morphological structures of the Venice Lagoon, as well as of many other tidal systems worldwide, which provide important ecosystem services, dissipate waves and mitigate erosion during storms. In the Venice lagoons salt-marsh areas are rapidly decreasing with rates that vary locally. Until now, many analyses have been carried out which mainly consider wind-wave erosion as a primary driver for salt-marsh retreat. In this thesis, the possible role of soil characteristics has been analysed. Salt marshes, in fact, are constituted by different sediment types, depending on their origin: Soil characteristics might contribute to increase or decrease the resistance of salt-marsh margins to erosion, and therefore might control the survival of these important landforms. Through a detailed analysis of the amount of organic matter, of the grain size, and of the density of the sediment within ten sediment cores collected at different sites in the Venice Lagoon, the relationship between lateral erosion and soil characteristics was investigated. Rates of salt-marsh retreat display a relatively weak correlation with soil characteristics such as particle size, bulk density, and organic matter content. The rate of erosion is strongly related to the incident wave power density, through a linear relationship