Nervous night for Ngongotahā residents as stream rises during heavy rain

It was a sleepless night for the Allerby family as the Ngongotahā Stream burst its banks in parts and rose dangerously close to their property last night.

The deluge that struck the Rotorua area left the Ngongotahā residents feeling nervous as they were told to prepare for evacuation.

It brought back memories of the one in 100-year flood in April 2018 that saw the evacuation of more than 30 homes - many of which were damaged - as the stream burst and gushed through properties around Western Rd.

Although yesterday's rain saw the stream rise by more than 4m, it only broke over the edges in some parts.

Herb, Hawaiki and Lee-Ann Allerby stand at the spot where the burst Ngongotahā Stream rose to on Monday night. Photo / Kelly Makiha

For Lee-Ann Allerby, her husband Herb and son Hawaiki, it was a rough night as they watched the stream, which threads through the rear of their Western Rd property, rise quickly.

"I was sh**ing myself, to be honest," Lee-Ann said.

"We were damn lucky it stopped raining when it did," she said.

Lee-Ann said she wasn't aware that the danger was so bad until she got a call at 8pm alerting her to the Rotorua Lakes Council's message, put out at 6.30pm, warning people to prepare to evacuate as there was the potential for the stream to overflow.

She said she immediately went outside and checked the stream, which is only about 20m from her back door, and it was swollen but not too bad. Within half an hour, it had risen several metres and burst its banks in some places on the other side of the stream.

The sudden danger saw Herb and Hawaiki try to free the flow of the stream, which was starting to get banked up with debris.

Lee-Anne said they held on to each other while they leaned into the torrents with a pitchfork to push away the debris that was thundering past.

"If they hadn't done that it would have been worse," she said.

The council issued another statement at 8.50pm saying the rain had eased and the stream wasn't expected to flood overnight.

Despite that, Lee-Ann said they were still on edge and her husband didn't go to sleep until after 3am as he kept checking the backyard to make sure the stream was subsiding.

Hawaiki and Lee-Ann Allerby show how far the swollen Ngongotahā Stream got to at the rear of their property. Photo / Kelly Makiha

MetService communications meteorologist Lewis Ferris confirmed 87.7mm fell in the 12 hours up to 4pm, with 112.2mm falling in 24 hours. The biggest downpour was between 2pm and 3pm when 20.9mm fell.

He said it was the wettest midnight to midnight 24 hours that had occurred in the area this year.

"It's rather rare that an urban area will record more than 100mm in a 24-hour period – a very wet day indeed."

Today Rotorua Lakes Council crews were still dealing with the aftermath. Crews were inspecting for damage, clearing slips, clearing grates and checking flooding sites for debris.

All rain and thunderstorm warnings for Rotorua have now been lifted. People are advised to keep up-to-date with the latest forecasts in case the situation changes and to monitor streams if they live nearby.

During the 2018 flood when a State of Emergency was declared, 167.8mm of rain fell over a 14-hour period.

An independent review panel released a report critical of the Rotorua Lakes Council and Bay of Plenty Regional Council in the lead up to the April 2018 floods.

Lee-Ann Allerby said the work the councils had done since 2018 by putting boulders along the steam bank on their side of the stream had worked "amazing" but hoped they would continue to do more work as more boulders on the other side of the stream to protect the walking track would be good.

Rotorua Lakes Council infrastructure and environment deputy chief executive Stavros Michael said the regional council had undertaken extensive stream repairs and maintenance works including tree removals, replanting and reinforcing embankments.

He said engineering interventions had been agreed with the community including diversion, overflow channels and raising parts of the local roads to increase stormwater capacity. This work was being done by the regional council.

"The floodway and further high flow bypasses are being worked on as fast as possible and as access to private land is obtained."

He said the regional council and Rotorua Lakes Council would provide another update to the community in the next few weeks.