Current river works

We are commencing stopbank upgrade works along the Lower Hinds River including removal and mulching of exotic trees from the stopbanks and replacement of fences. Necessary signage around the work area will be placed prior to the works commencing. Once the works are complete, the bank will be returned to a state that enables planting and habitat improvement.

This work is part of a larger project which is aimed at adaptation and repair of critical and aged flood protection infrastructure across Waitaha Canterbury.

• WHAT: Tree and weed removal and mulching, fence replacements
• WHERE: Approximately 600m along the stopbank between Surveyors Road and New Park Road on the true left side
• WHEN: Starting 19 March for about 2 weeks

Lower Hinds tree removal area of work

We will be removing four willow trees on the north-east side of the stopbank (between Mandeville Bridge and Williams Street Bridge) late April/ early May. There will be signage in the area before works start. 

Once the works are complete, the bank will be returned to a state that enables planting and habitat improvement (2026). 

Public access to the footpath and road between the Mandeville Bridge and Williams Street Bridge will be limited, managed by traffic control. Download the frequently asked questions (PDF file 164.32KB).

Removing these trees is the second stage of a larger project that strengthens our region’s flood resilience by upgrading flood protection infrastructure. In stage one we removed trees near Murphy Park to prepare for remedial work to the stopbank.  

• WHAT: Trees cut down to stump height and chipped on site
• WHERE: Between Mandeville Bridge and William Street Bridge identified in red on the map
• WHEN: Late April/ early May 2025 (this will take around three days).

Kaiapoi stopbank and tree removal area of work

As part of our initiative to improve river resilience in the Selwyn District we will be commencing maintenance works and willow tree clearing on the Hororātā and Waikirikiri Selwyn Rivers. These works aim to improve fairway capacity of the river and maintain trees to reduce flood risk and improve river habitats.

This will involve a large excavator, skidders and chainsaw crew working on the riverbank. Willows will be selectively removed (to retain habitat for fish, as well as ensuring some shelter of the river remains to keep water temperatures low, not all willows will be removed). Some sections of willow will be thinned and layered. Bank disturbance will be kept to a minimum and no native vegetation will be removed. Removed trees will be placed into burn piles within the berm and adjacent land and disposed of at a later date.

Measures will be in place to limit effects downstream, and works will be conducted in accordance with our Code of Practice. The area will be closed to the public and signs will be in place to clearly mark areas where work is happening.

WHAT: Willow Clearing and Tree Maintenance

WHERE: Hororātā River at Hororātā township, Waikirikiri Selwyn River at Greendale

WHEN: From Monday 10 March – 30 April 2025

Under consents CRC000746 and CRC235344, we will raise the weed barrier for collecting weed cut via a weed boat on the Huritini/Halswell River.

The barrier will remain raised until the end of the cutting operations, expected to be completed by the end of April 2025.

The barrier is located at the site shown on the map below near Motukarara and Greenpark Huts.

Weed cutting of the Huritini/Halswell River is an essential part of river maintenance to help control excessive macrophyte growth which raises water levels and contributes to flooding and drainage issues within the catchment. Weed is cut by our weed cutting boat, and cut weeds float downstream until they are collected and removed at the weed barrier.

We will be using the recently commissioned new weed barrier and winch.

• WHAT: Weed cutting, collection, and removal from river
• WHERE: Huritini/Halswell River
• WHEN: From 24 February until 30 April 2025

The pink shows the location of the weed barrier

We are commencing stopbank upgrade works along the Ōrāri River including removal of exotic trees from the stopbanks, replacement of fences and minor earthworks. Necessary signage around the work area will be placed prior to the works commencing. Once the works are complete, the bank will be returned to a state that enables planting and habitat improvement.

This work is part of a larger project which is aimed at adaptation and repair of critical and aged flood protection infrastructure across Waitaha Canterbury.

• WHAT: Tree removal, fence replacements, stopbank upgrades
• WHERE: Various locations along the Orari stopbank Burdon to Thatcher Roads
• WHEN: Starting Monday 24 February for three to four weeks

Location of work area

We will first survey the rivers to identify islands in the riverbed that require weed control and then spray targeted weed species growing on these specific islands. Target species for spraying are willows, gorse, alder, poplar, broom and lupins.

Signage indicating that spraying is underway will be placed at all spray operation refilling stations and public access points on the river. Public access will be restricted during operations.

• WHAT: Targeted weed control using helicopters for aerial spraying.
• WHERE: Please see the detailed maps below of the rivers.
• WHEN: Early February through to end of March, weather dependent.

Why do we control weeds in the riverbed?

Healthy waterways are central to a healthy environment. Our rivers are important places of cultural and ecological significance ki uta ki tai (from the mountains to the sea). Our waterways are vulnerable to harmful weed infestations, so we need to manage weeds for flood control and biodiversity protection.

Our staff and contractors carry out weed control measures in the open riverbed to help flood flows pass through and enhance biodiversity values. Left unchecked, invasive weeds are a significant flood risk, occupying the channel and forcing water towards neighbouring communities and farmland. Weed growth can also contribute to the loss of aquatic habitats and nesting areas for native birds.

Find out more about our weed control work, including the type and method we use.

Chatterton River - the area of works is outlined in red

Hurunui River - the area of works is outlined in red

Upper Hurunui River - the area of works is outlined in red

Kowhai River - the area of works is outlined in red

Upper Waimakariri River - the area of works is outlined in red

Mid Waimakariri River - the area of works is outlined in red

Lower Waimakariri River - the area of works is outlined in red

Waimangarara River - the area of works is outlined in red

Works are planned to remove crack and grey willow to improve flow capacity and reduce flood risk. Once removed, pest trees will be chipped and replaced with native species. 

• WHAT: Removing pest species and replacing them with native trees
• WHERE: A 300m stretch of the true right of Ōtūkaikino Stream, from Clearwater Avenue bridge
• WHEN: 17 February until the end of April

Ōtūkaikino Stream area of work

We will first survey the rivers to identify islands in the riverbed that require weed control and then spray targeted weed species growing on these specific islands. Target species for spraying are willows, gorse, alder, poplar, broom and lupins.

Signage indicating that spraying is underway will be placed at all spray operation refilling stations and public access points on the river. Public access will be restricted during operations.

• WHAT: Targeted weed control using helicopters for aerial spraying.
• WHERE: Please see the detailed maps below of the rivers.
• WHEN: Early February through to end of March, weather dependent.

Why do we control weeds in the riverbed?

Healthy waterways are central to a healthy environment. Our rivers are important places of cultural and ecological significance ki uta ki tai (from the mountains to the sea). Our waterways are vulnerable to harmful weed infestations, so we need to manage weeds for flood control and biodiversity protection.

Our staff and contractors carry out weed control measures in the open riverbed to help flood flows pass through and enhance biodiversity values. Left unchecked, invasive weeds are a significant flood risk, occupying the channel and forcing water towards neighbouring communities and farmland. Weed growth can also contribute to the loss of aquatic habitats and nesting areas for native birds.

Find out more about our weed control work, including the type and method we use.

Ashburton River - the area of works is outlined in red

Hekeao/Hinds River - the area of works is outlined in red

Selwyn River: Gillanders Road to Old South Road - the area of works is outlined in red

Selwyn River: Scotts Road to Bealey Road - the area of works is outlined in red

We will first survey the rivers to identify islands in the riverbed that require weed control and then spray targeted weed species growing on these specific islands. Target species for spraying are willows, gorse, alder, poplar, broom and lupins.

Signage indicating that spraying is underway will be placed at all spray operation refilling stations and public access points on the river. Public access will be restricted during operations.

• WHAT: Targeted weed control using helicopters for aerial spraying.
• WHERE: Please see the detailed maps below of the rivers.
• WHEN: Early February through to end of March, weather dependent. 

Why do we control weeds in the riverbed?

Healthy waterways are central to a healthy environment. Our rivers are important places of cultural and ecological significance ki uta ki tai (from the mountains to the sea). Our waterways are vulnerable to harmful weed infestations, so we need to manage weeds for flood control and biodiversity protection.

Our staff and contractors carry out weed control measures in the open riverbed to help flood flows pass through and enhance biodiversity values. Left unchecked, invasive weeds are a significant flood risk, occupying the channel and forcing water towards neighbouring communities and farmland. Weed growth can also contribute to the loss of aquatic habitats and nesting areas for native birds.

Find out more about our weed control work, including the type and method we use.

Ashburton River - the area of works is outlined in red

Upper Opihi River - the area of works is outlined in red

Lower Opihi River - the area of works is outlined in red

Orari River - the area of works is outlined in red

Rakaia River - the area of works is outlined in red

Lower Rakaia River - the area of works is outlined in red

Rangitata River - the area of works is outlined in red

Lower Waitaki River - the area of works is outlined in red

From November 2024 to early 2025, we are undertaking ground-based weed control and drone spraying across Central and South Canterbury. This work will be undertaken on fairways, access tracks and stopbanks around the rivers and drains listed: 

Central Canterbury spraying

• Ashburton Hakatere River 

• Hekeao Hinds River 

• Rakaia River 

• Waikirikiri Selwyn River 

• Ashburton Hinds Drains (UAV Drone) 

• Huritini Halswell River and Drains 

• Stopbanks across Central Canterbury (Selwyn, Ashburton, Hinds) 

South Canterbury spraying 

• Clandeboye Drains 

• Seadown Drains – beach to lagoon road 

• Waihi - confluence to the gorge 

• Temuka – confluence to Waihī 

• Stopbanks across South Canterbury 

Why do we control weeds in riverbeds, drainage schemes and stopbanks?

Qualified Environment Canterbury staff and contractors carry out weed control measures in the open riverbed, within our drainage channels and on our stopbanks to help protect our communities from flooding and enhance biodiversity values. 

Left unchecked, invasive weeds in these areas are a significant flood risk. Weeds bind river gravels into dense islands within the channel, which can obstruct natural water flow and redirect floodwaters onto riverbanks or stopbanks. This can cause erosion and puts critical flood protection infrastructure at risk. 

Weeds can also undermine the structural integrity of stopbanks and can smother and kill trees planted for flood protection. By removing weeds, we can increase the water-carrying capacity of the river and reduce flood risks. 

What chemicals do we use for targeted weed control?

Environment Canterbury uses glyphosate (a general broadleaf weed killer), triclopyr (brush weed killer), and surfactants under strict controls to control weed growth in riverbeds and berms under the terms of our resource consents CRC222040, CRC222041 and CRC222043. 

Glyphosate is widely used in New Zealand and other countries as a general-purpose herbicide, it is regulated in New Zealand by the NZ Environmental Protection Authority (EPA) and there are laws around its use. 

Products containing glyphosate are considered safe when the safety instructions on the product labels are followed. 

• For the EPA’s statement about glyphosate and information about how glyphosate is regulated in New Zealand  
• For more information about why and how we control weeds in rivers 

We are carrying out maintenance works on willow trees through a section of the lower Waikirikiri Selwyn River. This will involve a large excavator and chainsaw crew working on the riverbank. Willows will be placed into burn piles within the berm and selectively removed.

The first stage will involve identified trees at Selwyn Huts being floated across the river and disposed of on the opposite bank. The second stage involves the willow clearing programme moving upstream.

This work is being carried out to improve the fairway capacity of the river and maintain trees to reduce flood risk. Bank disturbance will be kept to a minimum and no native vegetation will be removed. 

WHAT: Tree maintenance and removal in the lower Waikirikiri Selwyn River

WHERE: Waikirikiri Selwyn River – Coes Ford to Selwyn Huts

WHEN: Mid December 2024 to March 2025