The civil defence exercise was based on widespread major flooding in the Waitaki district, but heavy rain actually fell in the upper Waitaki catchment, flooding rivers and streams including those at the head of Lake Ohau.
Omarama experienced a downpour lasting about two hours yesterday morning, which one long-term resident described as the worst she had seen.
The high country rain trapped 10 Waitaki Boys' High School year 10 pupils and three teachers in the Temple Valley.
They were caught on the north side of the Temple Stream, on the opposite side to the Temple shelter.
School rector Paul Baker said the party, on an annual camp, was safe and in contact with people on the other side of a stream which was impassable because it had risen quickly after heavy rain.
"People on the other side were even able to throw them extra gear they needed, but there was no question of trying to cross the river," he said.
The school party had plenty of gear, including tents, and had set up camp for the night. However, police had decided to fly them out, which was acceptable to the school because it could have been some time before the river subsided.
"The key thing in a situation like that is no-one panics and tries to force the issue. As long as they have the right gear, which they had, they could have stayed there for quite a while," Dr Baker said.
Omarama constable Les Andrew went into the area to check on the camp, and the decision was made shortly before 2pm to bring a Central South Island Helicopters' helicopter from Hampden to Lake Ohau to fly them out.
Sergeant Peter Muldrew, of Oamaru, who went with the helicopter, said the camping party was not in any immediate danger.
Police were concerned any attempt to cross streams, which had "treacherous" flows, could be disastrous.
The decision was made to fly the group to shelter at a Department of Conservation campground at the road end of the Temple Stream. Sgt Muldrew said the party made the right decision when it met the river not to cross, but to wait and seek assistance.
The civil defence exercise scenario was based on a "weather bomb" causing widespread flooding in the Waitaki district, similar to that in 1995, in Otago and Canterbury.
The council's emergency services manager, Eric Spittal, said there had been no major flooding event in the district since then and he felt it was timely to run an exercise.
The exercise scenario threw up a range of emergencies for civil defence to deal with, ranging from closure of roads, flooding of properties through to evacuation of homes and a major flood in the Waitaki River threatening the Waitaki dam.
The exercise included evacuating Kakanui School, with the co-operation of staff and pupils, and having to relocate the civil defence headquarters from Severn St behind the Red Cross Hall to Ardgowan School.
