The incredible 12 hr, 1 in 125 yr flood

If you love watching water, you'll appreciate this.
Amazing weather. The wind was forecast at 140 kmh across the tops, 120kmh locally. When a major low pressure sits on the alps, the rain drops en masse. Three things occur: warm air is sucked up into the leading edge of the front; heat is released by the front as the rain falls; and mass air mixing. Hence, it was +32C in Christchurch and 120kmh winds. It's a Nor'wester and is essentially the same as our chinook winds, right down to the arch across the sky. When the low on the west side of the alps is intense, it spills over the divide and pours rain on the headwaters of the eastern flowing rivers. And that's the day it was yesterday.
To start the day we drove 40 minutes west of town. It was sunny and hot, +27C at 9:30 am. By the time we were 30 minutes west, the sky was slate grey and pouring rain. The upper tributary to the main river was black - no point in even trying to go to the water we'd hoped, it was further up and not a chance of any clarity. We doubled back to town to fish a small creek.
We parked Serge's Pajero on the bank of a little stream and decided to try to escape the hurricane winds and tuck into a wee stream protected by willows - hopefully they'd block the wind. The intent was good. In 50 m I landed a nice 5+ lb brown. But, once we got into the canopy of willows, we realized our mistake. The freight train winds rained branches into the creek. Trout came spooking out of pools to tuck under shoreline roots. Pools were generally emptied as branches crashed into them. We were both quite anxious to get the hell out of there. We caught a few fish and looked at each other in fear as the last fish I was to cast to was interrupted by a large arm of a willow crashing into the pool, diverting flow. No need to die in a trout stream. We exited stage right. It was a brilliantly sunny day where we were with no rain, but the wind was simply too much for the trees.

 Below, AJ's fish is in the net but the line wrapped in 3 different sticks floating down the creek, blown out of the willows. The willow in behind had just fallen.

We walked back to the 4x4 to find that the big river parked just upstream from had risen dramatically. The family swimming the mouth of the creek had to move upstream a few times in short order, their clothes getting wet from the rising waters. The 4x4, had we stayed there, would have drowned in about 30 minutes. We drove to the bridge on the big river at the bridge and we could tell the river was coming up fast. Remember, it hadn't rained a drop on us all day. In fact, there were (and still are) out of control forest fires just south of us. But, below us, a spectacle of water unfolded.

Here's the first shot as we parked at the river lookout:

Similar view 5 minutes later:

A shot to the bridge: 

 We then noticed the local jet boat tour company noticed the impending high water, scrambling to get their boat out of the water:

 The tractor they use had a hell of a time on the loose gravel. It took some time to get traction in the undercut washed gravel to get out.

 Incredibly, less than 2 minutes after the tractor and boat got out of the river, the gravel bar they'd used literally disappeared under the raging torrent.

 The above shot was taken at 5pm. The shots below was taken the next morning at 8am.

As we watched the flood happen, people came to take photos... of the view. We pointed the river out to folks and we were looked at sideways. Just another Nor'wester front rain in the mountains. No biggie. Swim the river in the morning. Go for a fish. At home, a flood like that would be a 1:125 yr flood and everyone on the local fly fishing forums would be screaming about not fishing then claiming the river had been killed off. Here, it started and was over in under 12 hours. Our friend Serge guided up there today, sight fishing. Go figure. All this and it never did rain on us. Just blew like hell.
And this river chart shows what the flow did in that time frame: