Shoreline effects of vessel wakes, Marlborough Sounds, New Zealand

The science of vessel wake generation and propagation is well advanced, but the environmental effects of wakes are less well understood. The introduction of large vehicle and passenger-carrying fast ferries (HSC) in the 1990s resulted in numerous reports of environmental damage worldwide. In the Marlborough Sounds, New Zealand, regulatory agencies have struggled with the management of vessel wakes from both HSC and conventional vessels operating between the North Island and South Island. Gravel beaches along the route responded very quickly to the higher energy levels associated with the introduction of HSC, and there has been little change since that time, except in situations associated with geological instability. There has been no recovery of beaches towards pre high-energy conditions following HSC speed restrictions in 2000. Evidence of wake influences on very low-energy beaches in the far-field, over 7 km from the vessel path shows that long wave lengths associated with HSC can result in geomorphically significant waves and sediment transport. These findings are in accordance with other recently published results reported by other authors in the Baltic Sea.