Photos: Storm's severity even more unusual than first thought

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The flood at Waipapa Rd, near Kerikeri, yesterday. Photo / Kerry Sinclair

The storm that flooded Northland this week is more rare than first thought - as much as a one-in-150-years event in some areas.

It was initially thought to have been a downpour that might be expected about once in every 50 years.

The storm was moving over Coromandel and Bay of Plenty this morning, but MetService said the worst of the weather was now over.

Leading climate scientist Dr Jim Salinger said today that based on statistical models, the intense rainfall in Northland was the kind of event that occurred only once in more than 100 years.

"For Whangarei Airport for the 24 hours we are looking at greater than a 125-year event," said Dr Salinger, of the National Institute of Water and Atmospheric Research.

Over a two day period, for east Whangarei it was at least 150 years; Te Arai Point near Mangawhai, 150 years; and for Kerikeri, for one day, more than 125 years, and for two days, more than 150 years.

While based on past-climate data, Northland had suffered a one-in-more-than-100-years deluge, Dr Salinger said: "As the climate warms, this is the sort of thing we expect to see more often."

He added: "As climate warming occurs, the atmosphere can hold more moisture and therefore more rain falls and therefore what we have thought of under past-climate data as one-in-100 or more reduces and might be one-in-50 years or 1-in-20 years."

He said the February 2004 storm that flooded Manawatu did not produce as much rain in such a short period.

Storm easing

MetService said this morning that the heavy rain had now finished for Auckland and the Nelson Ranges and was easing in the Coromandel Peninsula. It should ease during the day in Bay of Plenty and this evening for northern Gisborne.

However, the Tairua to Whitianga Road was closed due to surface flooding.

Meanwhile, the flood waters were receding in Northland and the clean-up operation was under way.

About 150 people spent last night in welfare centres after flooding left roads and buildings washed away and cut power and phone services in some areas.

Telecom said it restored all main line phone and internet services to customers in the Far North overnight, including working through the night to repair a damaged fibre optic cable under flood waters at the Stone Store Bridge in Kerikeri.