Weather: New lake caused by huge landslide to be monitored as heavy rain expected to hit Tairāwhiti

A new lake formed by a landslide in the Waiorongomai Valley is being closely watched ahead of expected heavy rain, which is seeing Tairāwhiti's state of emergency extended.

The lake was created by a large landslide on privately-owned land, and is thought to be about 1km long in length.

Rain brought by cyclone Hale ravaged the region last week, causing floods, slips and power cuts. A state of emergency in Tairāwhiti was expected to be lifted at 10pm this evening, but will now remain in place.

Gisborne Mayor Rehette Stoltz told Morning Report scientists had only been able to map the lake by drone so far because of the weather conditions.

She said at this stage they believed the lake was safe.

"They will be keeping a close eye though to see if tomorrow and Thursday rain have any changes there or raise any concern, so our scientists are closely watching that lake," she said.

Gisborne District Council principal scientist Murry Cave said it was yet to be determined whether the lake was permanent or temporary.

Another lake formed in the same location in 2020, but it was much smaller and only lasted about a month, Cave said.

The council would be able to get a better idea of the width and depth of the lake once tomorrow's storm had passed through, he said.

The key point if the new lake failed was whether it failed rapidly or slowly, he said.

But at this stage, council has not identified any risk to nearby housing if it does.

"If it does fail, the flood level that would go through would be below any housing," Cave said.

He also did not recommend people visit the site.

"Anybody trying to go up there in a vehicle is very likely to get bogged."

MetService was also keeping an eye on a subtropical low moving toward the East Cape, which was expected to bring more heavy rain, as well as strong east to southeast winds, tomorrow and Thursday.

It has issued a severe weather warning for Gisborne from 1pm tomorrow until 1am on Thursday.

Between 70 and 90mm of rain was expected around Gisborne and north of Uawa.

There is also a heavy rain watch for Gisborne and south of Uawa from 3pm tomorrow.

A new lake has formed by a landslide in the Waiorongomai Valley, Gisborne.
A new lake has formed by a landslide in the Waiorongomai Valley, Gisborne. Photo credit: RNZ / Supplied / Murry Cave

Stoltz said the council was asking the community to be alert and have two-to-three days of food supplies on hand.

She warned people to stock up on supplies and move their animals to higher ground, ahead of heavy rain.

"If you have animals in the Hikuwai or Mangatokerau area please move them to higher ground, be prepared with supplies and stay tuned to the radio and the news, to our Civil Defence Facebook page, because we will update you, as MetService updates us," she said.

Her warnings were echoed by Tairāwhiti Civil Defence group controller, Ben Green, who said roading network was still vulnerable with multiple slips, dropouts and slumps. He warned people to stay away from danger spots.

"We have around 30 crews out there repairing roads and they're making good steady progress.

"There have however been reports of too many people driving past just to take videos and photos of the cyclone's damage.

"This makes it harder for our crews and puts them and the drivers at risk if they get stuck and need assistance. Please delay all unnecessary travel."

He added there were structural inspections were carried out on five bridges on local roads and there was more rain on the way.

Gisborne District Council principal scientist Murry Cave says it is yet to be determined if the lake is permanent or temporary.
Gisborne District Council principal scientist Murry Cave says it is yet to be determined if the lake is permanent or temporary. Photo credit: RNZ / Supplied / Murry Cave

Coromandel damage and beaches warning

Meanwhile, cracks in a major highway through the Coromandel Peninsula have forced the road to close.

Waka Kotahi found several cracks on the Kopu-Hikuai Highway yesterday following Cyclone Hale, which it worries could get worse.

Crews will carry out an investigation today.

Waka Kotahi said it would open one lane from 7am to 7pm tomorrow, with speed reduced to 30km/h.

The highway is one of just three options to travel to and from the region, and the most direct route from Auckland to major holiday spots like Whangamata and Whitianga.

The cyclone also caused severe erosion at several beaches around the Coromandel, which damaged dunes and public accessways.

Lifeguards are warning that shifting sands have created new rips in the water.

Surf Lifesaving manager for Eastern Region Chaz Gibbons-Campbell told Morning Report a a lot of sand was taken off the beaches through Coromandel and Bay of Plenty.

"Essentially the ocean's picked it up off the beach and dumped it back out, just offshore, which has created some new sandbars, a lot of new troughs, inshore holes that run parallel with the beach. It does cause a lot more rips and feeder currents, which can catch swimmers unawares," he said.

"It's important that people, when they come down to the beach, they take the time to assess those conditions. We still have patrols operating right through until Easter, and we're encouraging people to please swim between the flags and listen to the advice of the lifeguards."