LATEST: Raging rivers roared across the South Island yesterday, flooding Omarama, threatening bridges and blocking the main highway south.
Rain fell on already sodden high-country catchments, while melting snow turned the Rangitata, Waitaki and Rakaia rivers into torrents.
The Rangitata River near State Highway 1 peaked about 2.30pm, with water bursting through its southern bank, flowing across farmland and roads, closing the highway and forcing motorists to detour inland through Geraldine.
The road was reopened late last night after the river's level dropped, a southern police communications spokesman said.
However, drivers should continue to show caution as there was still some surface flooding as well as high winds, he said.
The South Island's main railway trunk line, closed by flooding yesterday, is likely to reopen this afternoon, KiwiRail says.
KiwiRail said a track inspection this morning revealed two wash-outs and staff had started repairs.
Five freight services had been delayed by the closure.
The Waitaki River was expected to peak last night. As a precaution, the 113-year-old bridges between Kurow and Hakataramea were closed until 7am today. Floods in 1995 weakened some of the wooden piers on the northern bridge across the Waitaki.
The old Waimakariri River bridge near Kaiapoi was also closed for a time yesterday.
Omarama was on the brink of a Civil Defence emergency yesterday, with 31 people evacuated from the camping ground at 5.30am, along with three residents living near the river.
A major slip closed the Lindis Pass, while a slip on the Mt Cook Highway caused problems.
State Highway 77 was closed to campervans and other high-sided vehicles because of high winds.
MetService severe weather forecaster Ian Miller said the weather system had brought massive amounts of rain to the West Coast and the Southern Alps.
The country's wettest place Cropp River inland from Hokitika had 440 millimetres of rain between midnight Friday and midnight Saturday, with another 106mm from then until 7am yesterday.
More than 300mm had fallen close to Mount Cook village and parts of the Mackenzie Country had about 70mm.
Meridian Energy spokeswoman Claire Shaw said vast inflows to the Waitaki hydro system had forced the power company to spill water.
"We started spilling Friday night at Benmore to put a hole in the lake, so when the expected rain came down we had somewhere to put it. Spilling at Aviemore followed pretty soon after that, and we started spilling at Pukaki today."
It was difficult to know how long the spilling would continue, she said.
Environment Canterbury southern flood controller Graham Sullivan said the Waitaki was a massive river, but an expected peak flow of 1800 to 2000 cubic metres a second would cause problems and surface flooding.
"It could well be the biggest flow since 1995.
"It's been a combination of three things a lot of snow, a lot of rain, and we already had a saturated catchment from a fortnight or so ago, and those things have combined to provide an enormous amount of water."
Another burst of rain is expected in the high country and the Canterbury foothills this morning, but should clear this afternoon.
Last night, MetService forecaster Mark Pascoe warned the weather was about to turn cold, with south to south-westerly winds this week bringing a chance of snow to low levels in parts of the south on Wednesday.
Snow was possible to about 400 metres in Canterbury and to 200m to 300m further south.
- with NZPA
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