KEY POINTS:
Tyronne "Bubs" Smith was driving across the plains of the National Park to dinner at the Chateau when he noticed the water.
One of his fellow passengers remarked on how high the river was.
"The funny thing was that there wasn't normally a river there. It was surface flooding."
Unaware of the tragedy as they went past the Outdoor Pursuits Centre (OPC), Smith was worried about the swollen Mangatepopo stream for another reason: its tiny population of rare blueduck or whio, that he monitors as a Department of Conservation ranger.
He hoped they had found shelter.
Smith and his mother were heading to the Chateau to welcome a Maori Land Court conference in his capacity as secretary of local hapu Ngati Hikairo ki Tongariro and hers as its "matriarch".
It was just as he sat down to dinner that he realised why he had seen a police car speeding past on the plain. A text message from his boss said: "Have you heard about the kids lost in the Mangatepopo?"
He was told: "They'll need you."
Smith left his buffet meal and went back to the centre. It was dark and there were three possible survivors still unaccounted for.
His encyclopaedic knowledge of the stream, built up from having it as an office over the past five years, was welcomed.
"I could hear voices in the dark saying: 'Primo, Bubs is here'," he said.
Smith became a police adviser to the search manager, the scores of pictures of the stream on his laptop meaning he was literally the eyes for the searchers. He was able to direct them to points in the river where he had cut out steps to get to stoat traps.
The knowledge was useful, but in the end they found only bodies.
Smith was one of a group who placed a rahui or ban on the stream that will be lifted once the victims' families have visited.
Smith is an expert on Tongariro rivers, having been born alongside one and travelled along others to trace the cultural history. He also liaises with river users such as the OPC and Genesis Energy on cultural issues from his position at Ngati Hikairo ki Tongariro and as a board member for the Tuwharetoa tribe.
Smith said even though he personally would not have gone in the stream for fear of flash flooding, that was based on his local knowledge and instinct. He said no fault could be placed on the centre or the instructor for doing so.
"It was one of those days where systems don't work," he says. "In looking for blame, we may be asking questions we aren't going to get answers for."
He said Ngati Hikairo had previously joined with the centre to defeat a bid by private interests to take water out of the stream from above the gorge.
Smith said he wanted the centre to continue taking students through the gorge and would advise any reviews of the tragedy that it should not be closed down.
"I know the value of what they are teaching the kids in that gorge. It is a beautiful experience. Risk is an inherent part of experiencing the outdoors."
