"That's when I got on the phone and called all my guys out and said something's happening, this is unusual, let's get going."
Mr Smith was holed up in the district council building for the next five days co-ordinating the response to the biggest flood on record in Whanganui.
"I got to sleep on the Monday. So it was probably the busiest and most intensive day(s) of my life."
For all the good work, he admits there are things that have been learned and will be done differently next time. "Miserable time for a whole pile of people and still is," he said. "Lots of things we can do better.
"If we had, instead of waiting for the data or expecting the normal model data, maybe sent somebody around on that Saturday afternoon to say 'we don't know what's happening, there might be an issue but we don't know', we could have saved a bit of heartache for people. Hindsight's a wonderful thing, though."
Overnight, as the river was topping its banks, Mr Smith and his crew worked through the night planning for the next 24 hours. On Sunday morning the priority was people and "making sure they were fed, housed, warm, dry, out of harm's way".
And then it was about getting into the rural areas by helicopter, checking on people and dropping off supplies.
"Whanganui getting cut off is something that we're not going to change," he said. "It happens every time we get a major flood. If there's an earthquake, bridges will go down. If there's a tsunami, coastal routes will get cut."
While the flood was over for most people after a couple of weeks, Mr Smith said the recovery had occupied the council emergency team for most of the year, not to mention those residents who spent months out of their homes. Some are still waiting to return.
"For 95 per cent of Whanganui, everything dried out, the houses were fine and they went back to business," Mr Smith said. "For those impacted, it's the equivalent of what those people in Christchurch went through. Their houses, their lives tipped upside down."