Lyttelton Port Company began an interim emergency dredging campaign in late April to restore its main shipping channel after an unusually high level of sediment infill caused by recent extreme weather events.
Since the completion of the Port’s scheduled maintenance dredging programme in November last year, nearly one million cubic metres of material have been infilled in the channel. This compares with a typical annual infill volume of between 600,000 and 800,000 cubic metres.
A significant contributor was the severe weather event on 27 March 2026, which deposited more than 430,000 cubic metres of sediment into the channel within a matter of days.
The subtropical low-pressure system brought very strong winds, large seas and long-period swell, especially around Banks Peninsula and the South Island east coast.
Prolonged periods of large sea states from January through April have further restricted shipping movements and accelerated infill.
In some areas, the loss of depth is now imposing tidal constraints on vessel movements.
The emergency campaign will use the Dutch dredging vessel Elbe and is expected to take three to four weeks.
Simon Munt, Chief Customer and Supply Chain Officer at Lyttelton Port Company, said the work was necessary to maintain safe and reliable port operations.
“The scale and speed of the infill we have seen over the past few months is well outside what we would normally expect,” said Munt. “Extreme weather events are clearly having a much greater impact on the harbour, and this interim dredging is required to remove high spots and restore safe channel depths for our customers.”
Simon Munt said shipping safety and supply chain reliability were the Port’s top priorities.
“Maintaining the shipping channel is critical for vessel safety and for keeping freight moving efficiently in and out of the South Island,” he said. “This work is about ensuring we can continue to operate safely while adapting to increasingly variable and challenging weather conditions.”
Lyttelton Port Company says abnormal weather patterns and large sea state events are becoming more frequent.
The Port will continue to monitor sediment movement closely and assess longer-term responses to increased climate-related impacts on harbour operations.
