Kaitaia's main highway south is likely to stay closed for days — or much longer — after torrential rain triggered a series of major slips.

At the height of the weekend's storm, which dumped as much as 200mm of rain on some areas in 12 hours, the Far North was almost entirely cut off with SH1 flooded at Moerewa, SH11 blocked by a slip at Opua, and SH12 underwater at Taheke.

Those points have been passable since Saturday evening but SH1 through Mangamuka Gorge remains firmly closed between Makene Rd and Victoria Valley Rd after the highway was blocked or undermined by slips at eight locations.

The biggest slip, just north of the summit, completely engulfed the road with about 5000cu m of earth and trees.

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There were two more slips on either side of the summit slip with one still moving late on Sunday.

While some slips can be fixed by clearing away soil and debris, at least one stretch of road has been undermined by a large underslip and may need significant engineering work to make it safe.

The NZ Transport Agency will spend the next few days assessing the damage before offering an estimated re-opening date.

NZTA Northland manager Jacqui Hori-Hoult said the detour route was SH10, which would add 20-30 minutes to most journeys.

She urged motorists on SH10 to take care north of Kaeo, where repairs continue after a 5m-deep tomo opened up on July 3, and at Taipa where road works are underway.

With school traffic also resuming as of yesterday she called on drivers to allow extra time for their journeys.

The closure means Mangamuka residents who work in Kaitaia have to drive the long way around until the road can be repaired.

They include Ringi Otene, who lives just south of Mangamuka Gorge but works at Archibald Motors on Kaitaia's main street.

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Instead of driving through the gorge — a trip which takes 30-35 minutes — she now has to drive via Broadwood and Herekino, a loop around the west of the Mangamukas which takes about an hour each way.

Otene said she was car pooling with another Mangamuka resident who worked as a dental technician in Kaitaia.

It was tough on people such as her nephew, who started work at 5.30am at Bell's Produce. He now had to leave home at 4.30am to get to his job on time.

Other residents who worked at Pak 'n Save in Kaitaia also had to set their alarm clocks early.

One of a series of slips in the Mangamuka Gorge described as
One of a series of slips in the Mangamuka Gorge described as "a forest moving onto the road". Photo / NZTA

The settlement of Mangamuka Bridge has a health centre, a well-used dairy, and is the headquarters of Tautoko FM, one of New Zealand's first iwi radio stations.

Mangamuka Dairy owner Eliza Kete said when she opened for business on Monday morning at first she couldn't work out why it was so quiet.

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Then she remembered the slip, which she described as ''a forest moving onto the road''.

While she had lost her travelling customers more locals were calling in to do their shopping because they couldn't get to the supermarket in Kaitaia.

Kete had to drive to Kerikeri for supplies on Sunday instead of Kaitaia, a longer trip but she enjoyed the change of scenery.

Mangamuka residents also had the option of driving to Broadwood for supplies.

Tautoko FM manager Cyril Chapman said the radio station was lucky in that it was barely affected by the highway closure.

Until recently some of Tautoko's radio hosts had travelled from Kaitaia but they had recently found work in Kaitaia, sparing them the drive over the ranges.

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With no through traffic Mangamuka was a very different place, Chapman said.

''It's beautiful and quiet. We usually get big trucks that roar past, the whole building shakes.''

The storm had even had some upsides for Mangamuka residents. The local vegetable grower, for example, had been unable to get to farmers' market in Whangārei on Saturday, so he shared his produce around the community instead.

Far North District Council chief executive Shaun Clarke said 160 local roads would need work to make then fully accessible and 86 would need significant slip repairs. Three bridges also needed fixing.

The repairs would cost about $2 million, he said.