Material and Environmental Factors Impacting the Durability of Oak Mooring Piles in Venice, Italy

Abstract

This study examines the rapid degradation of oak mooring piles caused by shipworms in Venice, Italy. In the last few decades, this problem has raised significant safety and environmental concerns, as the piles often need to be replaced every 18–24 months. The sound basic density and diameter of 22 oak piles were analysed after being exposed to shipworm attacks for 18–240 months to determine whether denser piles or larger diameters influence the rate of decay. This was performed to assess whether larger cross sections or higher densities of the piles could imply an increased durability against marine borers. The impact of environmental factors such as temperature, salinity, pH, and dissolved oxygen levels was also assessed. The results highlighted that pile density and diameter do not significantly influence the resistance against shipworms, while rising temperatures (+2 °C in the past two decades) may contribute to accelerating shipworm activity. These phenomena are worsened by the arrival of warm-water shipworms since 2013, exhibiting greater aggressiveness in wood degradation. Furthermore, the potential impact of storm surge barriers on shipworm activity remains an open research topic. Alternative materials and protection techniques introduced since 2015, such as polyurethane piles or metal stapling, face environmental and logistical challenges. Despite these alternatives, many new oak mooring piles are still installed in Venice without protection and are vulnerable to rapid deterioration. Addressing these issues requires multidisciplinary research to develop sustainable materials and preservation techniques for maintaining infrastructure in Venice.