Lyttelton Port Company (LPC) 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 program in November last year, nearly one million cubic meters of material have been infilled in the channel. This compares with a typical annual infill volume of between 600,000 and 800,000 cubic meters, LPC said.
A significant contributor was the severe weather event on March 27, which deposited more than 430,000 cubic meters 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, LPC said.
The emergency campaign will use Dutch Dredging’s trailing suction hopper dredger (TSHD) Elbe and is expected to take three to four weeks.