Wairoa flooding: Drains overwhelmed as 120mm falls in 24 hours

Wairoa is picking up the pieces from another flooding event in its streets as drains were overwhelmed by torrential Saturday rain.

Mayor Craig Little said unlike Cyclone Gabrielle, where the flood had come from the Wairoa River upstream, and June 2024, where the river bar had been closed, this one was purely down to the amount of rain and the inability of infrastructure to drain it away quickly enough.

No houses had flooded, but there was significant surface flooding across the town, with seemingly random streets affected “all over the place, he said.

“The river was in really good shape, the bar was working well, but this amount of rain is coming at a shorter time than it has been historically and we just can’t get the water away fast enough.”

MetService meteorologist Katie Lyons said Wairoa was by far in a way the place with the most rain in Hawke’s Bay on Saturday.

All up, 120mm fell in the 24 hours from 7am Saturday.

It included a severe thunderstorm that dropped 33mm in an the hour from 10am to 11am and then another that dropped 33mm from 11am to midday.

“Rain starts to feel heavy when it’s more than 5mm an hour so to have 66mm in two hours is absolutely torrential,” Lyons said.

Some residents were in a jovial mood, kayaking through the streets, and farmers did need the rain, but for most people it was “pretty annoying”, Little said.

“This sort of flooding has happened before, but if we keep getting weather events like this we need to look at what we can do to prevent it.

“We also really need to discourage people going for a look in cases like this, because the bow waves end up in people’s homes.”

Little said there would be a review to see why some streets flooded and others didn’t, including if some drains were blocked at the time.

“I’d also like to acknowledge all of the staff who got out there yesterday working to try to prevent things getting worse.”

Further south, it was a miserable day, but one without issue.

Napier saw 16mm in the same 24-hour period, while Dannevirke had 7mm.

Lyons said the weather would get considerably more settled heading into Monday, with sunny skies likely and some passing cloud.

Tuesday would be even better, and Wednesday would be pretty good, though there is a chance of some afternoon showers, with the majority of Thursday and Friday looking fine as well.

Lyons said the chance of thunderstorms reoccurring this week was looking very unlikely with the prevailing weather pattern.

There was the potential for 30C+ temperatures heading into next weekend, though it was too far away to be able to predict with certainty, she said.