The swollen river last night. Photo / Sarah Ivey
A "rain bomb" hit the Mangatepopo River causing the tragedy which left six students and a teacher dead, the head of the Sir Edmund Hillary Outdoor Pursuits Centre said today.
However, MetService defended its role saying that heavy warnings were issued before the tragedy.
Grant Davidson said the volume of water in the river rose massively from 0.5 cubic metres at 3pm to 18 cubic metres at 3.30pm.
By 4pm it had fallen back to 0.5 cubic metres.
Mr Davidson, who has worked at the centre for 25 years, said: "The equivalent of the Tongariro River was washing down the dry river beds.
"I have seen that amount of water but I have never seen it come down at that speed."
He added: "The outcome is tragic in this case. It seems to have been quite a rain bomb come through."
He said the drought conditions could be partly to blame as the heavy rain would have run off rather than soaking into the ground.
The area has rain 200 days a year and so the centre is geared up for wet conditions, he said.
Weather updates are faxed from MetService every morning but there was no heavy rain forecast for the area yesterday, he said.
MetService spokesman Bob McDavitt said this morning that the MetService had said on Sunday that the rainy weather would last all week.
A heavy rain warning for the area was issued on Monday and a severe thunder storm watch was issued from Northland to Taupo at 9am yesterday.
Mr McDavitt said the MetService had forecast 40-50mm of rain an hour and he said levels had been recorded between 30-50mm/hour in surrounding areas.
"It's sudden and it can happen (increased rain fall) and your heart has got to go out to their families."
He said the rain may not have occurred where the students were canyoning. "It may have hit further up and then run down."
The group of students went into the area at about 12pm and the trip usually takes two to three hours, going into the local gorges with an instructor.
It was intended as a team building exercise and the exercise has been carried out for 30 years.
The centre is carrying out its own investigation.
- with NZPA
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