We had new flood control gates installed in Paeroa in August 2018. It’s a huge improvement on what we used to have. The two gates slide together along a rail built into the road. It’s a huge time saver. The gates can be closed in about five minutes compared with the old setup where we had to take about an hour to construct a Lego-type wall. And that gives us a huge advantage in our flood protection level of service and reaction times. It also means we can respond to other duties during a flood rather than being here in lockdown building a wall.
The Ohinemuri River, which runs through the Karangahake Gorge, does flood a lot. Short, sharp rainfall events in the hills really gets this river up and running. If we didn’t have stopbanks in Paeroa, the town could go three metres underwater. Where the new gates are, there’s a gaping hole in the stopbank for the road to go through; the gates close that gap. It’s designed this way, and keeps flood waters away from buildings and public infrastructure, as well as productive farmland.
The water can come up very quickly – it can come up four metres in an hour – so closing the gates quickly is critical. Before we had stoplogs, nine pieces going across and three high, that took 10-12 men up to an hour to put up. It would be touch and go as to whether we could get it up in time before the river came through. We’ve had men waist deep in water; there’s been fun and games on Christmas Day with people having to come out and build the wall to protect the town; and you try getting that many men out of bed at three o’clock in the morning when it’s raining.
We partly put up this old Lego-style system, ready for full closure, three times in the last four years, but with climate change we reckon there’ll be a real need for these new gates in the future. We’re getting heavier localised downpours up in the hills. Our telemetry used to give us about an hour’s warning that water levels are rising in the gorge but the last couple of events we have only had about half an hour’s warning, so something is changing and we are having to react faster and faster. More rain, more water.
The gates were built by Flood Control International, a group in Europe who do flood protection all across the world. We’re very proud to have the biggest gates they have ever built. The gates run perfectly level across the rail on the road and when they touch we lower them down about 30-40 millimetres and that creates a perfect seal for minimal leakage.
The community are really happy we have done this. They have seen what we had to do with the wall and how quickly we can get the gates across. And we’ve bought ourselves another 50-80 years of flood protection. We’ve got to have flood protection – that allows everything else to happen in the Hauraki area.
The new gates across State Highway 26 hugely improve the reaction time to flooding in Paeroa.
"If we didn’t have stopbanks in Paeroa, the town could go three metres underwater."
It took 10-12 men an hour to build the old wall to protect the town from floodwaters. It would be touch and go as to whether it would get put up in time before the river came through.