Evolution of Tidal Flats in the Northern Part of the Po Delta: a Strategy for Future Building-with-Nature Management

In period of the 1950s-60s the municipality of Porto Tolle (RO) was hit by several floods. Agricultural fields were covered by water and many of them remained submerged since. However, such a phenomen had a positive impact on the deltaic landscape. As a consequence of the massive sediment injection into the system, this event lead to the birth of new tidal flats around the tip of the Delta. The evolution of these environments over 50 years has been studied as they may be taken as an example for future reconstruction of intertidal areas. The sediment distribution and the morphological evolution of a young tidal flat of about 10 ha located in the Northern part of the Po della Pila branch was studied by fieldwork since October 2018, including detailed topographic surveys, sedimentological analyses and a study of sediment deposition rates. The work is being logistically supported by the Veneto Region office of Rovigo. An extended tidal delta covers the central part of the flat. The granulometry is predominately fine (Silty clay and Clayey silt), except for the tidal delta area, where the sand percentage increases (Loam and Silty sand). This surface distribution is uniform down to ~10 cm under the sediment surface; instead, the sand percentage increases within the sediment column from ~10 to 25 cm next to the mouth. These observations suggest that the tidal channels are fed by sediment from the Po River branch. The tidal flat is divided into two sections: the Northern area is characterized by a high rate of accretion, while in the Southern area erosion is predominant, supporting the hypotheses that sediment is being redistributed without being lost. The work finally aims at identifying the optimal elevation for vegetation to establish and flourish and would support future restoration of these environments.