Waitaki District Council has declared a state of emergency following intense localised flooding that has inundated central Oamaru and forced dozens of residents from their homes.

Heavy rain overnight overwhelmed the district's stormwater system, flooding homes and businesses along Thames Street in the town centre. Fire and Emergency New Zealand received 70 calls overnight in the Waitaki area, responding to 41 incidents as crews worked to evacuate stranded residents and pump water from flooded buildings. The service responded to over 50 emergency calls since midnight.

Evacuations and emergency response

Emergency crews evacuated 18 people to safety at Oamaru Fire Station, while approximately 13 people and 4 dogs have taken refuge at a welfare evacuation centre set up at the Network Waitaki Event Centre.

Mayor Mel Taverndale said the council activated its Emergency Operations Centre and declared the state of emergency at approximately 4.30am when it became clear emergency services would struggle with the level of help needed.

Taverndale said the flooding was widespread and there were concerns about slips. At its peak, she said floodwater reached approximately 1 metre before emergency services began pumping operations.

Infrastructure damage

State Highway 1 has been shut between Seven Mile Road and State Highway 83, with through traffic diverted. Some cars were stranded on the flooded route.

Businesses along Thames Highway became waterlogged, with Fire and Emergency crews pumping water from affected premises including a Resene ColorShop. Taverndale said the district's stormwater system had been overloaded by the intensity of rainfall.

The council had used a digger to open up Oamaru Creek the previous day to ensure it was flowing properly and flushing out more quickly.

Residents flee rising water

Fire and Emergency shift manager Daryl Ball said crews had been working since 9pm the previous night, with Oamaru and Mosgiel experiencing the worst conditions. Ball said floodwaters on roads prevented crews from reaching some callouts.

Ball said there were lots of people still stuck in vehicles and houses. "If you can evacuate and you think you think you need to evacuate, evacuate early," he said.

One parent left Boundary Creek Road with his partner and children at 3am, narrowly reaching town. "It wasn't the river level that almost got me, it was the general surface flooding in my yard and around my car," he said.

Another mother evacuated with her three children — 10-year-old twins and a 6-year-old — after water on her driveway submerged both her vehicles to halfway up the doors, writing off both cars.

What comes next

Taverndale said rain was continuing and more was expected through until Wednesday, though it had eased off.