Shocking footage has emerged of a hillside turning into a river of debris and trees blocking a major North Island road.

Motorists are metres away as the hillside crumbles before their eyes.

One driver can even be seen nervously reversing as mountains of dirt and vegetation cascades onto the road.

State Highway 2 through Karangahake Gorge is now reduced to one lane following the large slip near Crown Hill Rd.

The road is under traffic management and motorists are advised to take extra care through the area and expect delays, Waka Kotahi NZ Transport Agency said today.

State Highway 25 from Waiomu to Ruamahunga was also closed due to a rockfall with incredible footage of both slips emerging on social media.

This comes as a fresh heavy rain watch was issued by MetService for Bay of Plenty, Coromandel, and Rotorua last night.

A front moving eastwards across the Bay of Plenty is now expected to “reverse direction” on Thursday and move back towards the Coromandel Peninsula, MetService forecast.

Thames Coromandel District Council said SH25 between Waiomu and Ruamahunga would be closed all day as geotech and abseil teams assessed the condition of the face.

“We expect an update this afternoon on estimated opening time, however, clearance works are not expected to begin until this afternoon at the earliest depending on conditions.”

A big slip came down on Tuesday near the Crown Hill Rd footbridge in the Karangahape Gorge on SH2, stranding some residents for a time but a video has come to light showing more slippage in the same area.

This slip fell over SH25 north of Waiomu on the evening of Feb 1 closing the road. More rain is forecast for the region. Photo / Mike Scott

The video posted on social media shows roading contractors watching the latest slip come down and motorists being waved through, sparking concerns about their safety from commenters.

A Waka Kotahi NZ Transport Agency spokeswoman told the Bay of Plenty Times the perspective of the video was a “bit deceiving” because it has been filmed from across the river.

“You can’t see the road or the distance the slip was from the workers, who were actually on the other side of the road. The earth that was captured slipping in this video didn’t even breach the closed lane as the attached image shows.”

A further part of the hillside slipped on SH2 in Karangahake Gorge on February 1. Photo / Waka Kotahi NZ Transport Agency

“These contractors are experts who are extremely familiar with clearing slips and slip behaviour and were at a safe distance from the activity.

“With the level of rain in the region, slips like this are forming all the time and there’s a well-known risk of new slips forming or slips reactivating when there’s already been a lot of earth come down.

“While the slips themselves can’t be controlled when they’re on the move, the road environment can be.

“In this case, the lane next to the existing slip site was already closed and traffic was being kept safe under stop/go traffic management while contractors worked to clear material from yesterday’s slip.”

The spokeswoman also said Waka Kotahi’s geotechnical engineers had visited the site and assessed the level of risk and an excavator was being kept in the gorge overnight so it can be used on-site as early as possible if required in the event of further slips.

Meanwhile, motorists are being urged to take care travelling through the Bay of Plenty and Waikato and expect delays after a number of slips, heavy rain and flooding had caused some road closures across the state highway network.

State Highway 33 between Okere Falls Rd and Taheke Rd had been under temporary traffic management on Wednesday due to slips in the area.

MetService said in the past 12 hours to 2pm on Wednesday, 14.5mm of rain fell in Tauranga, 27.3mm in Rotorua, 10mm in Whakatāne and 36.8mm in Waihī.

In the Coromandel district, there was more than double that amount of rain in the Pinnacles with 94mm in the past 12 hours and 147mm in the last two days.

Whangamatā experienced the second highest amount of rainfall with 68mm in the past two days, of which 60mm was in last 12 hours, compared to 66.5mm in Castlerock (in the Coromandel ranges) within a 24-hour period, she said.

Whitianga did not fare quite so badly, with 40.2mm in the past two days, more than half of which fell in the past 12 hours.