Underwater noise levels of pile-driving in a New Zealand harbour, and the potential impacts on endangered Hector's dolphins
Leunissen, E. M. and Dawson, S. M.
Impact pile-driving generates loud underwater anthropogenic sounds, and is routinely conducted in harbours around the world. Surprisingly few studies of these sounds and their propagation are published in the primary literature. To partially redress this we studied pile-driving sounds in Lyttelton Harbour, New Zealand, during wharf reconstruction after earthquake damage. That Lyttelton harbour is routinely used by Hector’s dolphins (Cephalorhynchus hectori), an endangered species found only in New Zealand, provided further context for this study. Steel piles of 0.61 or 0.71m diameter were driven using three different pile-drivers. Maximum calculated source SEL was 192dB re 1μPa2s @ 1m (SPL0-p of 213dB re 1μPa @ 1m). Propagation of piling noise was strongly influenced by harbour bathymetry and a rock breakwater near the piling operation. We calculated range estimates at which Hector’s dolphins may suffer temporary hearing threshold shift and behavioural change.
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