Offshore Dredger Sounds: Source Levels, Sound Maps, and Risk Assessment

Abstract

The underwater sound produced during construction of the Port of Rotterdam harbor extension (Maasvlakte 2) was measured, with emphasis on the contribution of the trailing suction hopper dredgers during their various activities: dredging, transport, and discharge of sediment. Measured source levels of the dredgers, estimated source levels of other shipping, and time-dependent position data from a vessel-tracking system were used as input for a propagation model to generate dynamic sound maps. Various scenarios were studied to assess the risk of possible effects of the sound from dredging activities on marine fauna, specifically on porpoises, seals, and fish.

An overview of fish bioacoustics and the impacts of anthropogenic sounds on fishes

“…Such activities generally produce sound that has the most energy at low frequencies ( i.e ., <1 kHz). Dredging, for example produces high levels of broadband noise (de Jong et al, ; Wenger et al, ) and is used to extract sand and gravel from the seabed and from lakes, maintain shipping lanes and to install pipelines and cables within the seabed. Activities onshore, including the passage of vehicles, may increase noise levels in the sea, lakes and rivers, especially if they generate substrate vibration.…”