Scientists are analysing data from hundreds of slips in the Nelson-Tasman region in an effort to forecast future risks.
And they're warning that the danger from current landslides might not be over.
Nelson's hillsides are now pockmarked with hundreds of slips.
The majority are in Nelson city where about 180 homes are still uninhabitable. Brett Daniel-Smith's house has been red-stickered because of a major slip.
"If the street behind us, and the one behind that, began to move then we'd be last man standing and it would come down onto the road and to our house," he said.
It's a situation geotechs are worried about, warning even a small amount of rain in cracked slopes could create major problems.
"If somebody goes back to reoccupy their home after it's been hit and more debris comes down then it's a life-risk situation," GNS Science engineering geologist Chris Massey said.
"There are properties where it is just deemed to be not safe at this time to go on their properties, and that's very very difficult," said Nelson Mayor Rachel Reese.
A difficulty scientists are hoping to reduce by combining data on landslide, rainfall, geology and land use into a landslide forecast model which shows what areas have a higher risk of slipping. It's something scientists want to develop for the entire country.
"We really want these models to be used to help decision-makers make decisions on where is a good place to live and where isn't a good place to live," Massey said.
Nelson City Council told Newshub it isn't changing any of its current housing developments - but that GNS Science's slip data will have an impact.
"The whole way we're going to be planning cities is changing, and that information we get from GNS now is going to be really critical to our thinking," Reese said.
Information that could change where and how people build in future or whether they can ever go home.
"We could end up losing our house altogether or not be able to go back there and we're being philosophical,"' Daniel-Smith said.
Because some tough calls might have to be made.
