One month's rain in a day + video

LATEST: Parts of State Highway 1 near Oamaru remain closed today as authorities wait for river levels to drop and flood waters to recede.

SH1 south of Oamaru has reopened, but the highway was closed at the Waitaki Bridge north of the town with diversions in place.

Motorists were advised to take extreme care and avoid travel where possible.

SH82 and SH83 were both now open but 56 local roads remained closed by surface flooding this morning.

Showers and sleet were forecast to continue today but high river levels were still retreating and the risk of further flooding was decreasing, a civil defence spokesman from Waitaki District Council said. 

Contractors were waiting for daylight to inspect roads and would reopen them if they are safe to pass.

Water supplies would be inspected today but many rural water supplies remained shut down and people in those areas were asked to conserve water.

Supplies of bread and milk were running low but normal supply was expected to resume today, the spokesman said.

Meanwhile, visitors were warned to stay away from a Ngai Tahu Maori rock art site south of Duntroon as a rock fall had blocked the site,

And the Otago Regional Council was investigating unauthorised propping up of floodgates along the upper Taieri river and had called in police, the Otago Daily Times reported.

Farmers were critical of the need to drop the gates and a lack of consultation, but a spokesman for the council said it was concerning that farmers were not dropping the gates properly which could be a hazard if river levels rose again.

One farmer said that if the gates had not been raised he may not have been able to save his stock.

Yesterday the Otago Regional Council warned that the flood risk would remain high on the Taieri Plains south of Dunedin, for several days.

Decisions over whether schools and kindergartens would reopen were expected by this morning.

Residents were asked to stay prepared and to make sure their emergency kits were ready.

Month's rain in a day but Christchurch escapes lightly

Christchurch has escaped with minor flooding after more than a month's rain fell in less than 24 hours.

The Avon River broke its banks yesterday afternoon and the Heathcote River came close to doing the same at high tide, about 4pm, and again last night.

Opawa, Woolston and Beckenham residents were watching the river anxiously last night, with heavy rain still falling, accompanied by gusty southerly winds and falling temperatures.

Snow, rather than rain, is expected to be the main problem over the next two days.

About 60 millimetres of rain fell in parts of Christchurch between Tuesday night and last night, taking the total fall since the storm system arrived on Monday to more than 100mm, about one-sixth of the city's average annual rainfall.

Rain was still falling on parts of South Canterbury and North Otago yesterday, although falls were lighter than on Tuesday.

Swollen rivers swamped paddocks and flooded roads, including parts of State Highway 1 near Oamaru, where about 200mm of rain had fallen since Monday.

Rain is predicted to continue throughout Canterbury and Otago into the weekend, but forecasters are turning their attention to lowering snow levels. MetService said last night snow was likely to fall as low as 300 metres in parts of Canterbury today, and to about 200m in Otago, as a sub-Antarctic southerly airstream became tangled in the system that brought the heavy rain.

Snowfall warnings were issued for today for Porters Pass, Arthur's Pass and the Lewis Pass, although snow was expected to settle only on the Porters Pass road, with up to 10 centimetres by tonight.

Severe-weather forecaster Andy Downs said last night there were signs of heavy snow in Canterbury tonight above about 400m, and further spells of steady or heavy rain along the coast.

"We've issued a watch but we may well upgrade that to a full warning in the morning."

Yesterday's deluge caused flooding around Christchurch and on Banks Peninsula.

Flooding forced the closure of Hunter Tce in Opawa, Wigram Rd in Sockburn, and Kinloch Rd in Little River, and road maintenance crews worked to clear several other streets along the riverside.

Other roads that the Christchurch City Council expected could be affected last night included Owles Tce, Richardson Tce, Aynsley Tce, Eastern Tce and Waimea Tce.

The Avon breached its banks in the afternoon around New Brighton Rd, from Avondale Rd to Anzac Drive, and flooded the road near the Wainoni bridge.

Wastewater overflowed into the Avon and Heathcote rivers at four sites yesterday.

City council water and waste manager Mark Christison said of the four spills, two were marginal and all were within resource consent conditions.

Wastewater infrastructure upgrades were "paying dividends" and had reduced the frequency of overflows during storms.

"We're getting a lot more wastewater and wet-weather flows through to the treatment plant that previously would have gone into the Heathcote River," Christison said.

"The city is, in fact, reducing the amount of wastewater that it puts into the river."

In the Selwyn District, emergency response crews assembled yesterday. Roads were closed near Springfield and Sheffield.

District council spokesman Chris Hewitt said the council was monitoring the situation.

"We're communicating with communities that are in our high-trigger areas, but at the moment we don't have any great concern, other than the weather," Hewitt said.

"We've got ponding and a little bit of surface flooding, but that on its own isn't an issue. It's the ability to get rid of that water."

Residents on rural water supplies were asked to conserve water as a "precautionary" measure.

The storm caused havoc on the roads, with cars stranded in metres of water, especially near Oamaru.

AA call-centre supervisor Mike Binis said the past few days had been "really, really busy".

Some people needed to be towed, while many had flat batteries from driving with lights on during the day, then forgetting to turn them off.

At 7pm yesterday, the centre had already fielded 1500 calls, more than it would usually experience in a day.

In North Canterbury, North Loburn resident Kaye Sanders awoke to an "instant swimming pool" in her backyard.

She prevented the water entering her home by digging a trench.

"We've had consistent rain up here and our drains just couldn't cope. It was a bit of a nightmare," she said.

It was the worst flooding she had seen in 15 years.

- © Fairfax NZ News