Morphological evolution of the Venice lagoon: Evidence from the past and trend for the future

During the last century, the Venice lagoon, Italy, has been experiencing a general degradation consisting of the deepening of tidal flats and the reduction of salt marsh areas. A conceptual model describing the long-term evolution of such lagoons has recently been proposed. According to the model, the long-term degradation consists of two steps: an initial salt marsh deterioration phase followed by a tidal flat erosion phase. In this work we test the long-term evolution model through the analysis of four different bathymetries of the Venice lagoon during the last century (1901, 1932, 1970, and 2003). The result of the analysis confirms that the recent past morphological evolution of the Venice lagoon has actually followed the proposed model and highlights a slower erosive trend characterizing the northern part of the lagoon compared to the moderately rapid erosion affecting the central southern part. This result enables us to infer the likely future evolution of the Venice lagoon as long as the present forcing conditions are maintained.