A state of emergency has been called on the West Coast due to torrential rain.
It comes after a West Coast bridge was washed away after hours of severe rain battered the region.
Mayor Bruce Smith declared the state of emergency due to "raised risk of life and injury for local residents and further risk to property".
A welfare centre has been set up in Haast Hall to host those whose properties have been flooded by "minor breaches" from the Haast River. About 50 people, mainly tourists, were staying at the hall.
The Waiho Bridge, which spans the Waiho River near the Franz Josef township, collapsed on Tuesday afternoon.
A New Zealand Transport Agency (NZTA) statement said hours of torrential flood waters carrying large amounts of rock and material downstream battered the bridge's support piers.
Franz Josef resident Logan Skinner said he was "disappointed and annoyed" after seeing the Waiho Bridge be washed away by a torrent of water.
Skinner said he warned authorities about three days ago that the northern end of the bridge's abutment was missing rocks and needed strengthening.
"On Sunday, I sent them an email and warned them about it. We said the north abutment of the bridge will go because there's rocks missing from it and it's at risk. They came back and said nothing was wrong.
"It's not like two years ago we warned them, it was three days ago ... there was machinery that could have done it and saved it. It was preventable."
Skinner said the damaged bridge would have a massive impact on tourism in the area.
"Not many tourists drive into a town and then drive back the other way. It's significantly going to hurt the tourism trade for the next couple of weeks," he said.
NZTA network manager Colin Hey said State Highway 6 would remain closed until the bridge and its abutment could safely be repaired.
State Highway 73, which links Canterbury and the West Coast through Arthur's Pass was also closed because of a slip at Candys Creek.
The status of the roads would be reassessed at 8am on Wednesday.
Alpine Glacier Motel manager Mark Gibson said the Waiho River was a "roaring current" when he saw it on Tuesday afternoon.
"It looks like the whole thing's gone apart from the uprights."
Although the raging torrent had taken out the bridge, Gibson said the township had not yet been evacuated.
In the 14 years he had been working in the nearby Fox Glacier township he had only seen the water of the Waiho reach the town once, he said.
"It's all heading in the right direction so we might be OK."
Torrents of rain lashing the West Coast are not expected to let up until Wednesday morning, with hundreds more millimetres possible in the ranges of central Westland.
At least one rural resident has been forced to flee their home and it is understood police are evacuating others from near Haast.
Westland District Council spokeswoman Diane Maitland said emergency services were on standby and preparing to make evacuations if the significant rainfall continued.
MetService said the band of heaviest rain was only slowly edging further north. It would be Wednesday morning before the rain began easing across much of Westland, and not until the middle of the day in Buller.
Head of weather communications Lisa Murray said up to 40mm an hour was likely in the ranges until midnight, easing to 15mm peak intensities until the severe weather warning lifts at 9am Wednesday.
NZTA network manager Colin Hey said crews were clearing the slips on the Fox Hills, near Franz Josef, but more slips were expected due to the intensity of the rainfall.
Westland District Council chief executive Simon Bastion said the Waiho River was "pretty much" at the same level it was when it broke its banks and caused $30 million worth of damage in March 2016.
Bastion said the council added extra protection along the north side of the Waiho River after the 2016 flooding, but it was possible the river could breach the south bank if the rain did not let up.
Smith said any flooding from a south bank breach could hit dairy farms and the airport, affecting tourism activities.
'SIGNIFICANT DISRUPTIONS' FOR TOURISTS
Fox Glacier and Franz Josef, which has about 3000 beds for visitors, relies heavily on traffic flow from the north.
Glacier Country Tourism chairman Ashley Cassin said the weather had caused "pretty significant disruptions" for tourists and businesses across the region.
About 2000 tourists were usually holidaying in the area at this time of the year and he expected they would be affected by the heavy rainfall.
"It's pretty clear [most] businesses will be affected in some way or another, with some being quite significantly affected, so financially it's huge."
Cassin said all scenic flights and helicopter flights were grounded until the weather had cleared.
"The net profit will definitely take a hit on days like today … [but] we're quite a resilient place and on a daily basis we deal with quite significant rainfall so it's not completely out of the norm."
Haast On The Spot Foodcentre owner Nicky Harris said the rain was "not too bad" about midday, despite the road having to be closed.
The rain had been torrential, but was easing off at lunchtime and she felt people were more prepared now than they were when ex-Cyclone Gita hit in February 2018.
That storm closed roads, caused slips and stranded hundreds of tourists in the tiny South Westland town.
Further south, a slip has affected State Highway 8 near the Bloy Rd intersection, between Lawrence and Waitahuna in Otago, and a heavy rain warning had been issued for State Highway 94 between Te Anau and Milford Sound.
River and lake levels in the Wakatipu, Wanaka and Hawea catchments rose on Tuesday and more rain was expected.
Otago Regional Council (ORC) natural hazards manager Jean-Luc Payan said the rainfall had been on the lower side of the predicted range, but the lakes were elevated and would stay high for a while.
"We're not letting our guard down while there's still the possibility of more rain, and ORC are continuing to closely monitor river and lake levels," he said.
All Ritchies bus services on the West Coast have been suspended for Wednesday.
STRONG WINDS FOR CANTERBURY
Gales were expected in many southern and central parts of the country on Tuesday, and into Wednesday further north.
The heaviest rainfall recorded by 5am Tuesday at a MetService weather station was at Milford Sound. Since the start of the rain on Sunday, 400 millimetres had fallen in the area, MetService meteorologist Stephen Glassey said.
That included more than 100mm in the five hours between midnight and 5am Tuesday – just over 30mm of rain an hour fell during two of those hours.
"That's the heaviest we've recorded where we have our weather stations," Glassey said. "It's likely it's probably even heavier than that up in the ranges."
A cold front started moving onto the country from the Tasman Sea early on Tuesday and would move north over the South Island during the next couple of days.
By midnight, the front should be sitting over Westland, and the rain should have eased to showers in Fiordland.
A period of heavy rain was expected in the northern part of the Canterbury headwaters and in northern Westland overnight Tuesday, while heavy rain could start falling in Buller late Tuesday night.
Winds could approach severe gale strength through to mid afternoon in Otago, and well into the night in the Canterbury Plains.