Ferry speed limit stopped shoreline damage

A decade after speed limits were imposed on ferry traffic in the Marlborough Sounds a marine biology report says shore life has recovered to the point where monitoring can be scaled back.

The Marlborough District Council began the monitoring 20 years ago when concerns were raised about the impact of fast ferries travelling through Tory Channel/Kura Te Au and Queen Charlotte Sound/Tōtaranui.

Council introduced a navigational bylaw in 2000 to limit boat speed and the height of vessels’ bow waves, for the sake of safety and to reduce the damage along the shoreline caused by wave action.

Now, after two decades, a report presented to Council’s Environment committee by Dr Kevin Parnell says, at most of 21 monitoring sites, the results suggest the shoreline erosion has either stabilised or returned to the state it was in before the fast ferries began.

In a companion report by marine biologist Rob Davidson, he referred to surveys of the sea life living at the shoreline and in the shallows showing increased numbers of invertebrate species and fewer numbers being cast up onto the shore by wave action. However, regular wave action from today’s ferries appeared to have limited the recovery of some bedrock and cobble sites along the beaches.

Mr Davidson said there was no doubt the fast ferries had a negative impact on biological life.

“Paua were being washed up onto the shore. It was the biggest adverse effect I had ever seen occurring along every shore exposed to the waves. Recovery has occurred but the recovery is variable and some places are still not back to their original state but there is no doubt the bylaw was a big success from a biological viewpoint.”

Council coastal scientist Dr Steve Urlich says the report’s findings show that Council’s intervention help to save part of the Sounds ecosystem.

"The monitoring shows the resilience of the marine environment. Appropriate and far-sighted management can put ecosystems back on the road to recovery. These results are encouraging, but there is much more to do to restore the ecology of the Sounds," says Dr Urlich.

Mr Davidson has recommended that the shoreline and biological monitoring be reduced to a bi-annual programme, noting also that it was important that it be maintained as there was little long term research on intertidal zones elsewhere in New Zealand.

ENDS

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