Another forecast Orange heavy rain warning for southern Westland is expected to delay the reopening of State Highway 6.
A section of the West Coast highway was closed between Haast and Lake Moeraki last weekend, following a major deluge which caused large slips and unstable ground around the road.
NZ Transport Agency/Waka Kotahi (NZTA) officially closed the road until this Sunday at the earliest, while work is done to clear the slips and stabilise some areas.
However, the latest forecast for more heavy rain has prompted the agency to review the reopening of the state highway.
MetService meteorologist Dan Corrigan said a low over the Tasman Sea was expected to approach the South Island tomorrow, with an associated rain-band and strengthening northerly flow spreading on to the country.
However, there is some uncertainty about the movement and timing of the low.
MetService has issued an Orange heavy rain warning from 11am tomorrow until 5am on Friday for the Westland District.
Up to 160mm of rain is expected, with possibly more in isolated locations. The heaviest falls could be up to 25mm per hour.
‘‘Streams and rivers may rise rapidly. Surface flooding, slips, and difficult driving conditions are possible.’’
A colder southerly flow with rain was expected to develop over the South Island on Friday and it was likely the heavy rain warnings would be extended.
‘‘It’s not expected to be as heavy as last weekend’s amounts, but there may be more impacts than we would normally expect because there has been a lot of rain lately, and there are a lot of slips around and some of the terrain is a bit unstable following the last event.’’
He recommended drivers take extra care in the area.
NZTA central region system manager Mark Pinner said the latest forecast for the area would cause delays because the ground was still saturated with elevated volumes of water flowing from slip drains, and the further rainfall would likely increase this further.
The area was now accessible by helicopter and inspections had been surveying the area, but ‘‘significantly more’’ inspection work was needed before teams could begin clearing the rockfall, Mr Pinner said.
‘‘We need to take this time to understand how the site might react to the rainfall since the weekend movement.
‘‘There will be teams onsite monitoring, but it won’t be safe to work on the slope in these conditions.
‘‘As soon as the site is safe after the weather clears, work will be underway again to make the slope safe.
‘‘Once the bluffs are made safe enough for crews to work under them, we’ll be able to provide a better indication of when the road may re-open.
‘‘Whether or not that will be Sunday or early the week after, will depend on whether the large and unstable rock mass adjoining this section of highway can be safely removed.’’
A further update would be provided as soon as that was understood, Mr Pinner said.
‘‘We do understand how important this route is for West Coasters and that it is a key route into and out of Otago for visitors, but we also need to protect people from the possibility of another rockfall.
‘‘We will need to monitor the road in coming weeks and months to be certain there is no more movement.’’
