From left: principal KDC floodgate project contract provider Barfoote Construction owner operator Trevor Barfoote, Kaipara Mayor Jonathan Larsen, KDC councillor Craig Jepson and Raupo drainage committee chair Ian Beattie during the floodgate construction in the Awaroa River. Photo / KDC
From left: principal KDC floodgate project contract provider Barfoote Construction owner operator Trevor Barfoote, Kaipara Mayor Jonathan Larsen, KDC councillor Craig Jepson and Raupo drainage committee chair Ian Beattie during the floodgate construction in the Awaroa River. Photo / KDC
New Zealand’s newest large agricultural floodgate is now operating near Kaipara’s Ruawai, protecting State Highway 12 and more than 8000ha of highly productive low‑lying farmland.
The pioneering 10m wide floodgate, near the mouth of the Awaroa River at Te Kowhai, is exceptionally large for an agricultural drainage scheme and helps preventKaipara Harbour invading the Raupō drainage scheme’s 8700ha.
Kaipara ratepayers paid $746,000 towards the $5.3 million floodgate on private farmland in the scheme’s southeast, about 10km from Ruawai.
The Government paid the $4.554m balance.
The floodgate on the scheme’s major tidal G canal was officially opened on May 3 by Regional Development Minister Shane Jones and local dignitaries.
Jones said the floodgate would strengthen flood resilience in the Raupō drainage scheme, protect productive land and SH12 and help future‑proof the district against sea‑level rise.
Its seawater invasion prevention also protects Ruawai township and surrounding areas, which are at or below sea level, by reducing flood risk.
The multifunctional floodgate, with fish passage, is described as the most complex agricultural drainage floodgate built in New Zealand.
Kaipara Mayor Jonathan Larsen said the project was a standout example of what could be achieved through strong partnerships and technical innovation.
“Ruawai is one of Northland’s most productive food‑producing areas, and this floodgate plays a critical role in protecting the land that so many livelihoods depend on,” Larsen said.
Minister for Regional Development Shane Jones (fourth from left) and Kaipara Mayor Jonathan Larsen (to Jones' left) cut the ribbon during the official opening ceremony for the Kaipara Raupō drainage scheme's floodgate Photo / KDC
The Government’s floodgate spend is its largest on a single agricultural drainage scheme floodgate in New Zealand.
Raupō Drainage Committee chair, Ruawai’s Ian Beattie, said the pioneering new floodgate was “bloody marvellous” and set a national benchmark.
“What looks like a simple structure is actually a project without peer in New Zealand.
“It has never been done before on this scale in a working environment so challenging. It pushed innovation in both design and construction and is a credit to all involved.”
The challenging environment included strong tidal flows racing in and out of the canal as the floodgate was built.
Staff worked up to 5m below high tide in a specially-made dry area. A temporary barrier of interlocking 12m deep steel panels created the protected area, allowing crews and machinery to work as water levels rose and fell around them.
The tidal canal floodgate has taken nearly a century to come to fruition. It was first included in the drainage scheme’s design in 1938.
“Shortly after that came the war, then post-war austerity and then it sort of got lost in the mix,” Beattie said.
Construction began in October 2024 and took about a year. The floodgate began working in September 2025.
“We’ve already seen its benefit in a moderate rainfall situation, during April’s Cyclone Vaianu when 80mm of rain fell on the Ruawai flats and 140mm in the hills behind,” Beattie said.
“The roads and paddocks that typically flood in that sort of rain cleared within 24 hours, rather than the usual two to three days.”
The official opening of Raupō drainage scheme's new $5.3m G canal floodgate on Awaroa River near Te Kowhai on May 3. Photo / KDC
The floodgate is about 2km from SH12 between Dargaville and Ruawai, an essential transport corridor for milk tankers, livestock, horticultural freight, farm supplies and emergency access.
It serves as a key detour route when other Northland state highways are closed.
SH12 was closed around Ruawai for several days in mid‑February 2023 after Cyclone Gabrielle flooding inundated low‑lying sections of the highway, cutting one of Northland’s key east–west routes.
Emergency services and councils have repeatedly pointed to its vulnerability.
The floodgate is intended to address that risk by controlling high tides at the southeast edge of the Raupō drainage scheme, and best managing floodwaters coming down from surrounding hills and sitting on the flats.
It operates automatically, opening when tides fall to release stored water by gravity and closing against incoming tides.
This speeds up drainage after heavy rain, reduces pressure on upstream stopbanks and lowers the risk of flooding across the scheme.
The floodgate spans Awaroa River, about a kilometre from the open Kaipara Harbour. It prevents seawater from travelling as far as 10km inland through the scheme’s drains.
It also means around 30km of farmland stopbanks inside the scheme no longer need to be built up to manage seawater.
A community open day will be held at the Te Kowhai Road floodgate on Thursday, May 14 from 9am-noon.
■ LDR is local body journalism co-funded by RNZ and NZ On Air.
