A group of 31 trampers rescued from a DOC hut in Fiordland have spoken of escaping with minor injuries after a slip crashed through the wall, crushing bunk beds.

A state of emergency has been declared in flooded Southland, including Gore, and dozens of people have been rescued from tracks in Fiordland today after being cut off by torrential rain.

It is unclear when State Highway 94 - the only road in or out of Milford Sound - would reopen, though that is not believed likely until next week.

Only two minor injuries have been reported since people began to be evacuated on Monday.

About 70 people were flown out of Fiordland from the Milford Road corridor and surrounding tracks. One of them was Josh Moffitt, who was tramping the Routeburn Track with five other family members.

They set out on Sunday and got no further than Howden Hut after finding a massive slip blocking the path to Mackenzie Hut.

The family were among about 15 people hunkering down at the hut with a ranger when another 15 people made their way over the slip.

Photo: Supplied / Brett Studholme

Moffitt said the rain was bucketing down and he hadn't slept a wink when rumblings began about 1.30am, followed by a slip that smashed into a corner of the hut, taking out eight bunks and causing one to pancake.

"Some people started to hear faint rumblings and some shifting sounds. And then maybe 30 seconds of really loud roaring, you know, bearing down freight train sort of sound, followed by splintering, crushing and then screaming," he said.

"One of the blokes had actually jumped up out of his bed as the noise started, which is super lucky because he was the one who was right on the corner where it actually penetrated the hut," Moffitt said.

"And he was able to as he jumped out, he grabbed a hold of his partner and pulled her out as well. So she did get a little bit bruised up as the bunks came down but by and large they were pretty unscathed and very, very lucky," he said.

Photo: NZTA

Moffitt said the entire group was left shaken and fearing what might come next with only headlamps to see through the pitch black night.

In the morning they realised how lucky they all were.

"The toilet block which is between us and another outbuilding - so probably five bays of toilet cubicles - was just non-existent, just wiped.

"Just gone. There was debris of it down in the river, and just as easily that could have been our whole hut," he said.

Moffitt, who still hopes to return next year to complete the track, said they were relieved to see the helicopter arrive this morning.

Brett Studholme and his husband David were part of the group that arrived at the hut, having climbed around a waterfall and making their way through a landslip knee-deep in mud to reach it.

"I was on the top level of a bunk, my bunk just fell down, collapsed. I jumped off and saw that my bunk had collapsed on a young woman under me so I quickly heaved up the bunk, and my partner and some people dragged her out from underneath where she'd been kind of crushed there."

David is an emergency doctor and was able to check people for injuries.

"She was pretty bumped, bruised, but nothing looked like it was broken," Studholme said. "Our bunkroom was smashed through. Other people heard this noise, were saying they thought it was thunder.

"Then the guy on the bottom bunk actually heard something hit the wall, jumped up out of his out his bed and this huge tree branch just came through his wall.

"If he hadn't have done that he would absolutely been taken out. He would've been gone."

Bunks were collapsed, walls were broken, and mud and branches were strewn through the hut, Studholme said.

"The whole hut was kind of on a lean, the main entrance-exit was blocked, you couldn't get out.

"A few of the support beams in the bottom floor were broken, cracked like a pencil."

It was 1am, with a long wait until daylight and hope of rescue, he said.

"We all quickly got into our wet-weather gear in case we had to go… Sitting in our wet clothes from the day's hike, wet socks, wet boots, for six hours.

"I was terrified. I was worried about more landslides coming down to clear us out completely, I was worried about the lake right in front of us that was rising so quickly.

"We were hearing through the radios that this was happening all over Fiordland at the moment."

He said when the sound of the helicopter came over, they were yelling with excitement. They were airlifted to a makeshift emergency centre in Glenorchy,

"They got us out so fast. They were landing, we were ready, six on, off it went… We were all out in half an hour."

Richard Sawrey who was rescued along with his wife and three children from McKerrow Island Hut on the Hollyford Track, said they had been forced to shelter on top bunks as the water level rose around them.

"The water levels around the island raised up to the level of our top bunk, just a metre below our top bunk. So we spent the last night on the top bunk, just hoping that the water would either go down or we'd be rescued," Sawrey said.

He said the group was cut off from the outside world with no one else at the hut and no satellite phone to call for help.

"We had to bash the sides of the walls out to let the water flow through, because the water was right up, right up into the top bunk and we were contemplating jumping out and getting onto the roof but we wouldn't last long up there."

He said the terrifying ordeal ended when they were rescued by helicopter about 8am this morning.

"We were winched up individually up into the helicopter from the water tank. We climbed out the broken window and onto the water tank and got winched up individually," Mr Sawrey said.

Hundreds of people remain trapped on the Milford Track and in Milford Sound, but they are believed to be safe. Authorities hope they can be evacuated tomorrow.