A local state of emergency has been declared in a Southland community due to concerns about threats to life and homes from erosion.
Heavy rain and sea swell has caused increased erosion of the banks at Bluecliffs township and landfill.
Emergency Management controller Simon Mapp said residents should be prepared to evacuate at short notice, but it was not required yet.
There are 18 properties there, although only six are home to permanent residents.
Mapp said two properties were "significantly impacted" but he was unsure exactly how unstable the land was.
Mapp said the swollen Waiau River was causing land to fall away from the banks of the township and its landfill.
"The declaration was made as a cautionary measure knowing that we're getting a king tide coming in over the weekend and also some rain in Fiordland that will influence the rivers."
He said the emergency declaration meant steps could be taken to open the river mouth bar to protect the properties and landfill from further erosion.
"At this stage we're building our technical understanding of the risks in the area and what might be possible to provide this community with some more time to manage their retreat."
The opening of the bar would be weighed against the risks. "This is a highly volatile area and that makes this a very difficult engineering task," Mapp said.
"I understand the residents of Bluecliffs will have some real concerns and frustrations. We're going to have a chat to them about that and offer them some support."
Southland District mayor Rob Scott said opening the Waiau River mouth to the east of the properties was a short-term fix aimed at buying time.
"That will direct the river flow to out to the ocean. That then takes the river out of the equation for doing the damage. The sand bar or gravel bar that's normally between the river and the ocean will naturally rebuild itself and provide protection from the ocean as well," he said.
Scott said people who lived at Bluecliffs would still have to make some tough decisions about their future and consider managed retreat.
"It's very complicated and a big job. It's important that the residents recognise it's a one-off operation," he said.
"No-one's ever taken on Mother Nature and won. We're kind of having an arm-wrestle with her at the moment. We need to be realistic about what the future holds."
The residents of Bluecliffs had experienced "the worst of both worlds", he said.
"The strong river flow coming down has had an impact on eroding away the land in front of those properties and also eroded away the sandbar, so they've had the worst of both worlds with the river coming through and the ocean coming through as well, and then over the last few days, we've had a whole lot of heavy rain."
The district council and Environment Southland had been monitoring the area since the September 2023 floods. "This enables us to move quickly to open up the mouth of the Waiau and protect the properties and landfill from further erosion."
"They're getting a double whammy," Scott told Checkpoint.
In the short-term there were plans to move the river back to the east.
Complicating the situation there was a landfill which had been exposed and it was thought there might be explosives in the ground as well.
"We were starting to clear the landfill and when we were made aware there might be explosives in there naturally we took 10 steps backwards very fast."
It was hoped moving the river back to the east would allow the sandbar to build back up and then the landfill issue could be reviewed and residents could focus on their future.
"It's not an easy path ... It's got a whole lot of risks attached to it as well but it's the best approach we've got in front of us."
RNZ Southland reporter Tess Brunton said Southland and Fiordland had received upwards of 60mm of rain in the past couple of days.
"That has caused that river to really swell."
However, the residents of Bluecliffs were "getting it from two fronts", she said.
"The heavy rain that's coming down the Waiau River is causing the land to fall away, but they've also got strong sea swells that are coming over the bar - that's the bar to the mouth of the river - and so that's also causing erosion."
It was unclear exactly which houses were under threat in the community, she said.
"There's been other reports that there's water lapping very close to properties. At the moment we're still working out exactly the state of these properties."
The residents had been talking about erosion for some time, she said.
"A lot of people think of it as a long-term process but it's really come to a head today."
Southland District Council started work to remove the community landfill last year which is eroding into the sea.
That work halted after reports of explosives being buried in the landfill.
The council was considering options to manage the risk and remove the landfill.
Alternative accommodation was available if residents felt unsafe.
The council was working with Meridian Energy on river flows.