Ship-wake induced sediment remobilization: Effects and proposed management strategies for the Venice Lagoon

• Shipping induced depression waves are likely a large factor in the erosion of Venice Lagoon shoals over the last 30+ years.
• Depression waves travel unimpeded onto shoals for at least 800 m, with enough shear stress to entrain sediment.
• Three simple management strategies are described to reduce the impact of these depression waves on sediments.
• This phenomenon and these management strategies likely apply to other narrow shipping channels around the world.

More than 3000 commercial vessels navigate through the Malamocco-Marghera Industrial Canal in Venice Lagoon, Italy in a given year, leading to an estimated annual resuspension of 1.2 × 106 metric tons of sediment. Hence, ship wakes contribute to the significant erosion of shoals in the central lagoon which has occurred over the last 30 years. Drawdown associated with the surface depression wave from successive ships induces sediment transport towards the shipping canal, where the cost of dredging amounts to tens of millions of Euro per year. Most ship traffic occurs near an industrial zone, resulting in substantial potential for resuspension of contaminated sediment. Thus, sediment resuspension by ship traffic in the Venice Lagoon has the potential for detrimental economic and environmental impacts.This paper illustrates the impacts of ship induced depression waves and discusses management options for mitigating those impacts, based on extensive observational data and analysis conducted in Venice Lagoon, Italy. This article helps to further the understanding of the processes that govern sediment transport along the shipping channel and employ this knowledge to develop specific management recommendations.A reduction in the navigation speed of ships, an increase in the distance between successive ships, and limiting navigation to tidal levels above 0.3 m from the local 1897 reference mean sea level can help to minimize these problems.