Think of a river like a hose that no one’s holding on to. The harder you turn on the tap, the more it jumps. One day the river flows here, and then it jumps over there, and then over there. We build stopbanks to tame the hose, but if we get an event that is bigger than a stopbank is designed for then that river could jump in a heartbeat.
The south end of Lake Taupō is the business end of the catchment. Here, the Tongariro River, Waiotaka, the Tauranga Taupō and the Waimarino all empty into the lake. You can see what a massive deposition area this is. It’s 5000 hectares, some 1600ha of wetland, which for the last 1800 years or so has been filling with volcanic ash and sediment. All these rivers contribute. It’s a natural process.
We’ve gone and built our lives around rivers and lakes because it’s a nice place to be, flat and fertile too, but we are living here on this massive, big, dynamic floodplain. We have built in places where perhaps we shouldn’t have. We are trying to control nature as best as we can but what if we have a 1 in 1000 year event? Imagine what that looks like! We have no comprehension of these forces.
Regional council is charged with addressing this issue. They are stuck between a rock and a hard place. People are not so keen to protect themselves from a 1 in 1000 event. There isn’t the money for that, and so the council has to make some hard calls about what levels of protection are acceptable.
Here, our schemes have been designed for 1 in 100 year flood events, and all told we have had three of those in the last 120 years: in 1906, 1958 and 2004. And we are likely to get more as the temperature heats up and the intensity of events ramp up. For every 1 per cent increase in atmospheric temperature you fit another 8 per cent of water vapour up there and that’s opportunity for intense, intense rainful. We will change our views on what is a 1 in 100 year flood. It may be a 1 in 30 or 1 in 20 year flood next century.
The Lower Tongariro scheme was built when Tūrangi was built in the 1960s, to protect the settlement and the river from the waste treatment plant. I live next to a stopbank and if it gets overwhelmed, I get it. It breached in the 2004 event and all the water burst through. Where I live became a lake. I lost a car. We had water through the house half a metre deep. My insurance premiums went through the roof. The channel capacity is designed for 1.5 million litres of water every second, all coming under the bridge. You can hear boulders the size of cars grinding down the river when these big floods are happening.
The Tauranga Taupō scheme protects people, State Highway 1 and the bridge at the river mouth of the Tongariro-Taupō River. It’s younger and very, very complex. Most of the protection was post 2004 because it was such a devastating flood. When there is a big event they open up a bypass when the river gets to a certain height. The water is diverted into a spillway so it bypasses the settlement, otherwise it’d be see you guys later.
Most people wouldn’t have a clue about the schemes or how they work. They know they pay rates for it but unless you have been here a long time you don’t see floods. People don’t value it as much as they should because they haven’t seen the devastation. It’s not until something happens that you hear all about it: Why am I not protected?
Lake Taupō Zone
Includes the Tongariro and Tauranga Taupō flood protection schemes.
Includes 25 floodgates and 7.5km of stopbanks.
Protects Tūrangi, Oruatua and Te Rangiita.
Replacement cost of about $7.76m.
1949 aerial image of the Tauranga Taupō River and the many paths it's taken.
"We are trying to control nature as best as we can but what if we have a 1 in 1000 year event? Imagine what that looks like."
Sandbags were used to protect homes from the rising Tauranga Taupō River in the 2004 weather event.