A new floodgate planned for the Raupo drainage scheme can proceed after the Kaipara District Council agreed, in their December meeting, to redirect funding from the Te Kopuru stopbank project to build the floodgate.

Floodgate G, to the south of Ruawai, is one of two floodgates that were initially planned. It will protect a large area of highly productive land from being inundated with salt water. Stopping the salt water at the entrance to the canal minimises the need to raise around 30km of stopbanks along both sides of the canals.

Council applied to MBIE for $20 million to build two floodgates to protect the Raupo area and raise 13 kilometres of stopbanks between Dargaville to Te Kopuru. Of the $6 million received, MBIE allocated $2.5 million for the two floodgates, and $3.5 million for the stop banks.

Consolidating the funding will enable the Council to complete one floodgate and avoid the need to pay back the $700,000 already spent on floodgate design to MBIE. MBIE requires funding to be returned if councils are not able to complete projects described in their contracts.

Mayor Craig Jepson says building floodgate G was the best way to draw value from the funding we have.

“We’ve focussed funding where it will protect the largest land area, and the most significant infrastructure. That includes State Highway 12, which provides a vital link from Dargaville across the district,” says Mayor Jepson.

Anin Nama, General Manager Infrastructure Services, says none of the projects have been stopped and the Council will be in a good position to continue the stopbank and floodgate projects when future funding becomes available.

“This decision allows us to progress an integral piece of infrastructure to protect some of Kaipara’s most productive farming area. Completing floodgate G also builds on the work we are already doing with the Ruawai/Raupo community through our Adaptive Pathway pilot programme, planning how to adapt to rising sea levels,” says Anin.

The total cost of the floodgate is expected to be around $4.6 million. The remaining $1.4 million is to be spent on raising approximately 2 kilometres of the stopbanks to a height of 3.5 metres.

Editor notes

About the Ruawai Adaptive Pathways project

Ruawai Adaptive Pathways is the adaptation planning pilot project for Kaipara District Council.

Council is supporting the Ruawai community to develop a plan to prepare for, and respond to increasing coastal hazards, flood hazards and sea level rise. The community is coming up with long-lasting approaches to adapt to climate change that are good for the community and good for nature.

Read more about the Ruawai Adaptive Pathways project

The Raupo drainage scheme

The Raupo Drainage District covers an area of approximately 8,700 hectares of highly productive fertile land surrounding the small settlements of Te Kowhai, Nau Mai, Raupo and Ruawai. It is protected by a network of 70kms of stopbank, 140kms of canals and drains, 52 floodgates and one
flood pump. To minimise the need for extensive stopbank upgrades from increasing tidal impacts and to prevent saltwater intrusion into these canals, the proposal is to install floodgates.

The floodgate structures will protect Councils assets and the strategic State Highway 12 from rising river levels. The exclusion of salt water from these canals also allows for strategic freshwater storage within the catchment area.

Dargaville to Te Kopuru Stopbanks

The existing stopbank between Dargaville and Te Kopuru protects an area protected by a network of 12.7kms of stopbank, 154kms of canals and drains, 22 private and 9 district floodgates. Around 27% of the stopbank length is 3m in height or above. The remainder varies between 2.5m and 2.75m in height. The upgrade of the existing stopbank requires compacted soil placed on the 3 banks to increase the height to 3.5m, the minimum height now required by Council to provide flood protection for the next 100 years.

Current works will see approximately 2km of the existing banks increased which aims to protect the community from inundation from storm surges and future river level rise. Further funding will be required for works on the remaining 11km of stopbank.

Local communities and Iwi from the three local Marae have been involved and consulted since the inception of the project.

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