"It's down at the south end of the port, which is not a wharf, but a retaining wall adjacent to what was a road that provided us with access to the port.
"That's what has eroded and significant amounts of it has fallen into the sea. The sea wall is actually eroding a little bit at a time already. When it gets a bit further, we'll have to think about it in terms of what structure we put back. But for the moment, we've got some other things we need to sort out first."
An oil boom has been put in place to make sure debris does not flow out into the harbour.
The port holds close to 200 different sized containers.
"There's only one that's gone in the harbour," he said. "The bigger ones are quite a bit further away and they're safe."
The fallen container belongs to pest control company Kwikill Environmental Services.
Owner Mike Hermansson said much of what was inside was equipment used for fumigation purposes such as sheets and fans.
He guessed the equipment was worth around $10,000.
"I've got insurance, but it's still a hassle. We'll probably be able to salvage some things, like the sheets ... But the fans, once salt water gets into them they won't be worth anything."
Mr Hermansson said he had not been out to see the damage for himself, as authorities had asked the public to stay away.
Regional harbourmaster Mike Pryce said: "The actual container terminal and the cranes seem to be all right, as far as I know. It's just the south end that's causing us problems."
