Civil Defence said the Brooklyn stream had breached its banks, which led to the decision to evacuate about 20 homes in the nearby coastal settlement of Riwaka, northwest of Nelson.
Paul Shattock from Civil Defence Nelson-Tasman said the Motueka Recreation Centre was open for residents needing shelter.
The flood water had flowed on to paddocks and farmland. Shattock said on Friday evening that homes had not been flooded yet, but the evacuations were happening as a precaution.
MetService forecasters said that from 11am Friday to 9pm Saturday the rainfall could reach volumes up to 25mm an hour in Marlborough, Nelson and some parts of Tasman.
In that period between 150mm and 250mm of rain could fall about the ranges, and 100mm to 150mm elsewhere.
Nelson Mayor Nick Smith urged residents to remain vigilant. While the intensity of rainfall in the latest forecast was reduced, he stressed there were still orange heavy rain warnings in place.
“There is still the risk of flooding, there is still the risk of landslides, and we’re still wanting the community to take precautionary steps.
“We particularly want people to keep a close eye on the highway conditions report from Waka Kotahi, as there is still a risk of travel disruptions.”
Smith said the highways most at risk were the main links to Marlborough, Tākaka and the Motueka Valley.
Nelson Tasman Civil Defence members were on alert and would be closely monitoring river levels and rainfall to determine if they need to activate.
“We’ve been making arrangements for emergency accommodation in the worst-case scenario,” Smith said.
The mayor also called on residents to ensure their properties were prepared for the heavy rain, advising them “to make sure those gutters and things are prepared”.
“We’ve closed some of our reserves and playing fields just because of - when they’re saturated, the risk of damage to those.”
Northland
In Northland, an orange rain warning was posted for all of Friday until 6am Saturday. Peak rainfall rates of up to 25mm an hour were possible, especially in thunderstorms, MetService said.
Steady heavy rain that fell through much of Thursday had already brought down small slips and led to road closures.
Northland Civil Defence communications specialist Zach Woods told RNZ’s Morning Report that by Friday morning the far northern and western coastal parts of Northland, including Kaitāia, had seen the most rain so far.
“Looking at what we’ve received and what we’re due to receive, we are through the worst of it, but we are asking residents to just continue to monitor the situation with us and ... if anything does happen to stay prepared and look out for the roads,” Woods said.
“There’s definitely a high amount of saturation in the soil, and that’s why although this heavy rain continuing to come isn’t as heavy as we’d normally be concerned about ... just because it is such a long event and there is so much moisture already there - that’s why we have to just continue to monitor this closely.”
Woods said the hydrology team at the Northland Regional Council would continue to keep a close eye on river levels through the orange weather warning.
Taranaki rain warning extended
The orange heavy rain warning for Mt Taranaki has been extended for 24 hours until 9am Saturday.
The region was expecting a further 90mm to 130mm of rain in addition to what had already fallen, Taranaki Emergency Management Group controller Todd Velvin said late on Friday morning.
Peak rates up to 30mm an hour were expected on Friday night.
Velvin said that overnight from Thursday into Friday morning the region did not get as much rain as had been expected, but authorities would continue to monitor the situation into the weekend.
He said as storms like this one become more common it was important to be prepared, stay informed and listen to official advice.
Buller and Westland warnings
MetService also placed a heavy rain watch over the Buller area until noon on Sunday and an orange heavy rain warning over Westland until 3am on Saturday.
It warned those in Westland that some coastal areas could have up 80mm of rain, and up to 110mm about the ranges. Peak rates there could reach 25mm an hour.
Where to stay up to date on the changing conditions:
