Number of slips on local Whanganui roads doubled since last year

Whanganui District Council roading crews have responded to more than double the amount of slips on local roads than they did last year. Photo / Bevan Conley

The amount of slips on Whanganui roads has doubled in a year.

Whanganui District Council's senior roading engineer Matt Williams said wet weather from December 2021 to June 2022 had resulted in an unusually large number of slips.

"Crews have responded to significantly more landslips around Whanganui's local road network than in previous years."

In the year to June 30, 2022, there were 390 slips on Whanganui's local road network.

That's compared to 161 slips in 2020/21, 112 in 2019/20 and 95 2018/19.

There have been 35 since July this year.

The increase was mirrored in the region's state highways.

Waka Kotahi New Zealand Transport Association spokesperson, Megan Heffield, said there had been 57 slips, dropouts, washouts and rockfalls on State Highways 3 and 4 in the Whanganui region in 2022.

In 2021 Waka Kotahi recorded 39 slips on the same stretches of road, with 34 recorded in 2020 and 28 recorded in 2019.

Heffield said there likely had been more than what had been recorded.

In the past two weeks, State Highway 4 between Raetihi and Whanganui has had to be closed overnight twice due to slips, with the most recent closure between 10am and midnight on Tuesday.

The number of landslip claims laid with Toka Tū Ake EQC (The Earthquake Commission) in the region has also increased this year.

A spokesperson said EQC has received 10 landslip claims in Whanganui this year, six of which are currently open and being processed.

In previous years, EQC received three landslip claims in 2021, five in 2018, three in 2017, two in 2015, and none in 2020, 2019 and 2016.

Both Williams and EQC said the increase in slips this year was due to extra rainfall.

MetService meteorologist John Law said so far it had been a wet year for Whanganui, though not to a record breaking degree.

He said so far for the year Whanganui had seen an above-average amount of rainfall, with 738mm of rain recorded, whereas an average year would record around 680mm of rain to this point in the year.

"It's by no means the wettest part of the country, but it is still wet," he said.

So far this September, 48.8mm of rainfall has been recorded in Whanganui.

In August, 79mm of rainfall was recorded, which is below the average amount for the month of 92mm.

However, in July 129mm was recorded, which is above the average for the month of 95mm.

Law also noted across July 20 and 21, over 25mm fell each day, which he said was a huge amount of rain to fall over one day.