Flood resilience projects

Why is this work important 

This work protects the nearby landfill and the properties that back onto River Road from the risk of flooding caused by the Ruamāhanga Awa moving horizontally across the landscape over time.  

What does it involve? 

The project formed the second stage of work at this site and was focused at the confluence of the Waipoua and Ruamāhanga rivers.  We used 6,500 tonnes of rock to build a 150-metre-long revetment (a layer of large stones placed at an angle on the bank to slow down erosion and keep the river from undermining the land) and a rock groyne (large rocks placed at right angles to the riverbank to further guard against erosion).

The work secures the True Right Bank (that’s the right-hand side when facing downstream – the direction of the flow) of the river, providing flood protection to the landfill and those properties that back onto River Road.  

Estimated start/end date 

This project is complete.

Why is this work important 

This work provides added protection to the landfill site.  This project is the third stage of the Ruamāhanga River Scheme and the Te Kāuru Upper Ruamāhanga Floodplain Management Plan. It represents the final stage of the fully consented Ruamāhanga River works. 

What does it involve? 

The involved building a further seven rock groynes to connect with the revetment and groyne built as part of Stage 2, above.  

Estimated start/end date 

This project is complete.

Why is this work important 

This work is needed to prevent further erosion of the riverbank and stabilise the existing riverside walking track at the point where the river flows under the road bridge on SH2.  

What does it involve? 

675 tonnes of rock were used to create a revetment on the True Left Bank (the bank on your left-hand side when facing downstream of the river). 

Estimated start/end date 

This project is complete.

Why is this work important 

Erosion on a bend in the river created a very steep slope/drop-off of land at the river’s edge. This was threatening the stability of existing industrial buildings and facilities on nearby properties. 

What does it involve? 

The chosen solution involved installing a series of rock groynes and a revetment to stabilise the lateral movement of the river, along with vegetation management inside the bend. 

Estimated start/end date 

This project is complete.

Why is this work important 

This project will protect the true right bank of the Waiōhine Awa at Fullers Bend from erosion. The aim is to minimise the risk of the river abruptly changing its course or abandoning its current one and carving a new one when in flood.  The work aligns with the recommendations of the Waiōhine Rakahanga River Plan. 

What does it involve? 

Groynes will be built along the true right bank (the bank on your right-hand side when facing downstream of the river) of the awa to protect against further erosion.

Estimated start/end date 

Enabling works have begun. Project due to be completed in 2026.

Why is this work important 

The Ruamāhanga River has eroded laterally, undermining the riverbank and eating into the edge of the existing Awaroa spillway sill. The sill controls the volume and speed of water entering the spillway, especially during periods of high flow, thereby reducing the risk of downstream flooding. 

What does it involve? 

The plan is to reposition the sill further back from the river’s edge and build 10 rock groynes of 200 tonnes each in front of it. This will deflect the flow of water away from the sill and reduce further lateral movement of the river channel. 

Estimated start/end date 

Enabling works have begun. Project due to be completed in 2026.

Why is this work important 

The raw water supply is an important lifeline for the people of Masterton.  Erosion control along the true left bank (the bank on your left-hand side when facing downstream of the river) of the Waingawa River will protect this important community asset and increase the town’s flood resilience. The work aligns with the recommendations of the Te Kāuru Upper Ruamāhanga Floodplain Management Plan. 

What does it involve? 

Groynes will be built along the true left bank of the Waingawa Awa to control riverbank erosion.  

Estimated start/end date 

Enabling works have begun. Project due to be completed in 2026.

Why is this work important 

This work is needed to protect the southern end of the Hood Aerodrome runway from the gradual erosion that is taking place on the true left bank (the bank on your left-hand side when facing downstream of the river) of the Waingawa Awa.  The work aligns with the recommendations of the Te Kāuru Upper Ruamāhanga Floodplain Management Plan. 

What does it involve? 

We will build a revetment along the bank of the Waingawa Awa where it passes the southern end of the aerodrome runway. 

Estimated start/end date 

This project is complete.

Why is this work important 

There’s a need to protect the base of the Otāki cliffs which are under threat from erosion of the true left bank of the Ōtaki Awa. These works are included in the recommendations of the Ōtaki Floodplain Management Plan. After construction, the construction works will be monitored over time to assess the need for additional upgrades. 

What does it involve? 

Over 8,000 tonnes of rock will be used to build a revetment and groynes along the true left bank (the bank on your left-hand side when facing downstream of the river) of the Ōtaki Awa where it passes the cliffs. 

Estimated start/end date 

Enabling works have begun. Project due to be completed in 2026.

Why is this work important 

This sill (along the Tawaha Floodway (which crosses the State Highway 53 at Jenkins Dip) plays a crucial role in managing overflows from the Ruamāhanga River into the Tawaha floodway, thereby enhancing flood resilience for the surrounding communities.

However, an accumulation of sediment in the adjacent river channel, berm and sill, along with vegetation growth, is hampering the spill from working as it should.  

What does it involve? 

The works will involve the reconstruction and / or levelling of the sill and repairing the low spots on the surrounding stopbanks to create a more consistent spill and flood water management system. 

Estimated start/end date 

This project is complete.

Why is this work important 

This work sits within the Lower Wairarapa Valley Development scheme.  It was the last stage of a wider project to remove the old stopbank. This gives the river more room to move, which in turn will reduce flooding.  

What does it involve? 

We removed the old stopbank, regrassed the berm and completed the planting plan using willow poles and natives.  

Estimated start/end date 

This project is complete. 

Why is this work important 

This project seeks to enhance fish passages within the Wairarapa region, by developing or rehabilitating structure(s) that are crucial for flood protection while also supporting fish migration objectives.  

What does it involve? 

We’ve identified several prospective locations that would benefit from installing a fish bench. This will enable migrating fish to swim upstream, providing suitable rest points along the way. Specially shaped rock has been acquired for the fish bench and delivery is underway. Construction will be thoughtfully guided by Te Ao Māori methodologies. This deliberate integration fulfils the project's core objective of establishing a dual-world fish passage, harmoniously blending Western scientific knowledge (Te Ao Pākehā) with traditional Māori wisdom (Te Ao Māori) to achieve a comprehensive and culturally appropriate solution.  

Estimated start/end date 

Enabling works have begun. Project due to be completed in 2026.

Why is this work important 

This work aims to reline the riverside face of the existing stopbank along the true left bank (the bank on your left-hand side when facing downstream of the river) of the Waingawa Awa. This will reduce the flood risk to the southern section of Masterton. These works are included in the recommendations of the Waingawa Awa portion of the Te Kāuru Upper Ruamāhanga Floodplain Management Plan. 

What does it involve? 

We’ve begun enabling works, which have included vegetation clearance across the site. The next phase will be detailed surveys and a thorough contaminated land assessment, scheduled to begin in May 2025. This assessment will be crucial to understanding the environmental conditions and informing subsequent remediation strategies, ensuring a safe and sustainable development.  

Estimated start/end date 

Enabling works have begun. Project due to be completed in 2026.

Why is this work important 

This project will offer added protection to the the treatment plant should the stopbank be breached. The project is part of the Ruamāhanga River scheme and Te Kāuru Upper Ruamāhanga Floodplain Management Plan. 

What does it involve? 

Design for the first phase of construction works involved building a retaining wall and concrete pad for the relocation of the transformers at risk from flooding. These works are now complete and ready for the relocation of the other transformer by the asset owners. The next phase of work will address the risk to the main site. 

Estimated start/end date 

Enabling works have begun. Project due to be completed in 2026.

Why is this work important 

The Te Kāuru Upper Ruamāhanga Floodplain Management Plan outlines the erosion protection that can be created by planting native trees and shrubs along waterways to protect and restore riverbanks.  Planting the buffer (the area between the active change and the outer river management line) can help protect against erosion as well as slow down and trap flood waters.   This project will see fast growing native and exotic planted at the rivers’ edge. These will then weave into the banks. 

What does it involve? 

Young plants from our nursery are being carefully nurtured and monitored, ensuring they are robust and ready to be transferred into their permanent locations. Simultaneously, significant progress is being made on other crucial fronts. Ongoing negotiations with iwi are focused on exploring collaborative co-design options for the planting project, ensuring the integration of cultural values and traditional knowledge. Productive discussions continue with landowners, working towards mutually beneficial agreements and fostering a collaborative approach to the project's implementation. 

Estimated start/end date 

Enabling works have begun. Project due to be completed in 2026.

Why is this work important 

The Whakawhiriwhiri stream is in the existing Lower Wairarapa Development Scheme. It flows through an overland floodway.  The stream does not have capacity to convey the ponded water which creates flooding hazards for surrounding landowners.   

What does it involve? 

Land ownership of the site is fragmented across numerous parties. The programme team is diligently addressing individual landowner concerns with tailored solutions. An initial phase of construction work, to improve the flow of water along the Whakawhiriwiri stream by removing blockages, has been completed. The next phase is now being developed and will be implemented in collaboration with landowners. 

Estimated start/end date 

Enabling works have begun. Project due to be completed in 2026.