Year-long construction of the $1.25 billion Ovation has just begun in Germany, but operator Royal Caribbean is understood to have already pencilled in three round trips from Sydney during the summer of 2016-17, calling at about six New Zealand and Australian ports.
Port Otago chief executive Geoff Plunket said Ovation's length meant it could not navigate the lower channel in its current configuration.
However, preparation of a technical report on channel-widening had been started by staff, with a public consultation to follow, before a resource consent application was lodged before the end of the year.
''Yes, this widening is just for cruise ships ... This size of ship is a new addition to the market,'' Mr Plunket said yesterday.
Port Otago had existing 20-year consents for deepening and widening the channel for container ships, carrying up to 8000 20ft equivalent containers, but to widen the channel further for the longer cruise ships required new consenting, he said.
''At the time [of the earlier consenting] these size cruise ships weren't even being built,'' Mr Plunket said.
It was only the length, and not the draught of the 168,666 gross tonne Ovation that was significant for using the harbour.
Ovation could be moved within the existing ''swing basin'' at Port Chalmers, and accommodated at the Beach St wharf, without any wharf additions, Mr Plunket said.
Two bends in Dunedin's lower channel, between Harington Point and before Port Chalmers, would require widening to accommodate ships the length of Ovation.
While the technical study was still to be compiled, Mr Plunket believed the two bends would not need of a lot of spoil removed.
''Fine tuning'' the channel was not expected to affect adjacent sandbanks.
The Ovation has capacity for nearly 5000 passengers.
It will have a glass observation capsule rising 91m above the deck, bumper cars, a circus school, a skydiving experience and 18 eateries, including a Jamie Oliver restaurant.
