Sediment transport in a tidal inlet: the case of the Lido Inlet, Venice, Italy

Abstract

Tidal inlets provide a connection between the ocean and bays, lagoons, marshes, and tidal creek systems. Two hydrodynamic factors are dominant in the long term evolution of a tidal inlet: wind waves, that are mainly responsible for re-suspending sediments, and tidal currents, that maintain the main inlet channel by advecting sediments away from the inlets. These two factors determine to a large extent the direction and magnitude of sediment transport. Tidal inlets, however, are often radically modified by human-driven intervention (for example for navigation or protection purposes). This is the case of the three inlets of the Venice Lagoon, Italy, that are now the main construction site of a mobile barrier system for the protection of the historical city of Venice from floods. In September 2014, an experiment was set up in one of the lagoon inlets aimed to quantify the bedload transport inside the inlet channel over a tidal cycle. To obtain a bedload transport estimate, we carried out repeated bathymetric surveys inside the inlet channel during a tidal cycle using a high resolution Multibeam Echosounder System. The tidal currents and water column transport were measured with ADCP calibrated by water samples. At the same time, sediment traps were deployed at the channel bottom and grab samples were collected. The preliminary results of the experiment show evidence of net transport over a tidal cycle. Comparing repeated bathymetric surveys over different years we find substantial changes in the inlet channel morphology.

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ORCID for Hachem Kassem: orcid.org/0000-0002-5936-6037

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