Current river works

Targeted aerial weed control

We will be surveying the specified rivers to identify islands in the riverbed that contain weed species, before undertaking targeted spraying from a helicopter. Signage indicating that spraying is underway will be placed at all refilling spray operation areas and at public access points on the river. Public access will be restricted during operations. An aerial flyover will be conducted prior to spraying to identify any river users.  

• What: Targeted weed control using helicopters for aerial spraying   
• Where: Please see the detailed maps below of the rivers
• When: From mid November to December 2026, and from early February to March 2027 (as weather permits)

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. Our waterways are vulnerable to harmful weed infestations, so we need to manage weeds for flood control and biodiversity protection.  

Environment Canterbury 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 flood 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 weed control work, including the type and method of control we use.

What chemicals do we use for targeted weed control? 

We use herbicides (glyphosate and triclopyr) under strict controls to manage weed growth in riverbeds and berms under the terms of the resource consents CRC222040, CRC222041 and CRC222043.

Waikirikiri / Selwyn River spray area

Hakatere / Ashburton River spray area

Ōhau River spray area

Pūkaki River spray area

Takapō River spray area

Weed Cutting in the Huritini / Halswell River

What: Weed Cutting, and Weed collection / removal from River

Where: Huritini / Halswell River

When: From Monday 12 January 2026 – Until 30 April 2027

Environment Canterbury is planning to commence work under consent CRC000746 & CRC235344 to raise the weed barrier for collecting weed cut during maintenance works on the Huritini / Halswell River.

The weed barrier will be raised for this work from Thursday 5th November 2026 with river weed cutting operation via the weed boat to commence as soon as the barrier is set up.

The barrier will remain raised until the end of the cutting operations, expected to be completed by the end of April 2027. 

The barrier which is located at the site shown on the map below, on the Huritini / Halswell River 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 the Environment Canterbury weed cutting boat, and cut weed floats downstream until it is collected and removed at the weed barrier.

This season Environment Canterbury will be using the recently commissioned new weed barrier and winch.

Ashburton Hakatere River north branch gravel extraction

What: We are extracting gravel from the riverbed for to help with flood protection.

Where: The north branch of the Ashburton Hakatere River upstream from Walkhams Road. See map.

When: Mid-October 2026 to end of March 2027

What to expect: This work is taking place on the north branch of the Ashburton Haketere River, upstream of Walkhams Road. It includes removing gravel from the riverbed, where severe aggradation (build-up) of gravel has decreased the flood capacity within this narrow reach of the river. Removing it will improve flood resilience through this section of the river. The gravel will be stockpiled and available for other construction projects of significance to the local community.

Geotechnical investigations along the Ashley Rakahuri stopbanks

What: We’re carrying out ground investigations at 10 locations along the primary stopbank. This will involve drilling and digging test pits to help us better understand the stopbank and the ground beneath it and inform future flood protection improvements. This work is part of a wider project to strengthen flood resilience along the Ashley Rakahuri River. Find out more about the project and the options we’re exploring.

Where: Along the primary stopbank, from the Ōkūkū confluence to the estuary.

When: Work will begin on Monday 2 November.

What to expect: You may see drill rigs, excavators, and work crews in the area. Sections of walking and cycling tracks may be temporarily closed while work is underway. Please follow any on-site signage and stay clear of active work areas.

If access through private property is required, affected landowners will be contacted beforehand to discuss access arrangements.

Tree clearance work at Waihi River, Waitui Drive, Geraldine

What: Tree clearance, mainly sycamore trees with some willow removal

Where: Waihi River beside Waitui Drive, Geraldine

When: November to December 2026

Starting November 2026 for approximately 3-4 weeks

We're removing mostly sycamore trees, along with some willow, from a section of the Waihi River beside Waitui Drive in Geraldine. This is the first stage of work to widen the river channel and improve the river's ability to carry flood flows through this area.

During the work, people can expect to see heavy machinery operating on site and an increase in truck movements along Waitui Drive as timber and other material is removed.

For safety, signs will be installed at river access points and access to parts of the river and work area may be temporarily restricted while work is underway.

What: Maintenance will be carried out in three native planting areas within the berm, along with targeted weed control across approximately 6.6 ha. Weed control will focus on reducing invasive and exotic vines around the planted areas and supporting existing flood protection vegetation. A bike and walking track runs alongside the site. Signage will be placed to advise members of the public when spraying and weed control operations are taking place.

This work will be carried out over a minimum of three rounds. The first round will take place this month, the second at the start of summer, and the third at the end of summer. If required, a fourth round will take place in autumn. Maintenance and weed control activities are weather dependent. Crews will work on dry, non-windy days. Wider weed control will take place during late spring and summer. Members of the public can expect to see work crews operating within the berm at various times over the coming months.

Where: True right berm of Hakatere River, above Lake Hood, along the public walking and bike track.

When: September 2026 to June 2027

Otukaikino Creek Confluence - Targeted willow control

Spring 2026

What: We will carry out targeted spraying and manual control of regrowing willow.

Where: Ōtūkaikino Creek confluence, near the walking and cycling track in Waimakariri Regional Park.

When: Late September to end of December 2026, weather permitting.

What to expect: You may see work crews and temporary signage in the area while work is underway. Please follow any on-site instructions.

Temuka River berm vegetation mulching and tree clearance – Winter 2026

WHAT: 

Environment Canterbury will be carrying out vegetation mulching and tree clearance in several areas along the true left berm of the Temuka River.

The work is designed to improve the river’s ability to safely manage flood flows and increase the resilience of the berm during high river events.
Some areas will also be cleared in preparation for planting several thousand native and flood-protection plants.

These plantings will increase vegetation cover and diversity, helping to strengthen the berm over time.

WHEN: 20 July to early-November 2026

WHERE: Temuka River berm, near Temuka Domain and Temuka Golf Course

Temporary signage will be installed before work begins, and some areas will be closed to the public while work is underway. We ask people to follow all signage and stay clear of active work sites for their safety.

Channel maintenance and native planting on Twenty One Drain

WHAT: We will be undertaking drainage channel maintenance and site preparation works within a coastal drainage channel between the Ashburton and Rangitata rivers.

The works involve clearing and processing woody material, improving access and preparing the site for riparian native planting.

Native planting will take place later this winter in August to increase indigenous vegetation cover and long-term shading and habitat values.

WHEN: July - December 2026

WHERE: Twenty One Drain, downstream of Ocean View Road

• Removing selected trees and vegetation
• Clearing debris from the river corridor
• Processing material on site at a skidding site off Highfield Road
• Removing usable wood from site
• Chipping and spreading smaller material on site

• Reduce fire risk to nearby homes, visitors and recreation areas
• Limit the spread of wilding conifers along the river corridor

• Machinery operating in the river corridor
• Increased vehicle movements near access points including Highview Lane
• Temporary noise and disruption
• Temporary restrictions to some public access areas to keep people safe

Rakitata/Rangitata South Branch stopbank construction

Where: South Branch of the Rangitata/Rakitata River, to the west of SH1, near Arundel-Rangitata Rd 

What: We will be constructing new stopbanks at three locations (shown in Figure 1) on private land. The works  also include realigning an existing stock water race and installing two new culverts. The gravel used to construct the stopbanks will be taken from the main branch of the Rakitata/Rangitata River, north of the site.

These works are designed to improve flood protection for the local community by reducing the risk of overland flooding when the South Branch is flowing. This will help protect nearby homes, farmland, and 
key infrastructure, including State Highway 1 and the railway line. Construction materials may be transported along public roads, and traffic management will be in place where required.

When: April 20th to end of October 2026, during dry weather.

Forestry Harvesting at ‘Grassy Banks’ site on Ōpihi River

WHAT: We are harvesed around 27 hectares of poplar forest on the southern bank of the Ōpihi  River. The areawas harvested for timber and will be replanted in another forestry crop, the species is to be confirmed.

Parts of the river, including access tracks and roads, will be closed to the public while harvesting takes place.

Once harvest is complete, controlled burn of forestry slash and some mulching will take place.

WHERE: The poplar forest is on the Southern side of the Ōpihi River at the top of Seadown Road, between the SH1 bridge and Waipopo Road. 

WHEN: The harvesting crew are aiming to start on the week of 2 March 2026. The operation is expected to take 15 weeks.  Controlled burning of slash started in the first week of November.

WHY: These poplars were planted for flood protection. As they have matured, harvesting them is now the best way to manage the trees and make use of their value. The income generated will be reinvested into flood protection work across the Ōpihi catchment.

Courtenay Stream floodgates construction

WHAT: Replacing the Courtenay Stream floodgates in Kaiapoi

WHERE: At the confluence of Courtenay Stream and the Kaiapoi River

WHEN: Work begins the week of 2 February 2026 and is expected to be completed by end of December

The current floodgates were built in the 1940s and are now due for renewal.

This upgrade is co‑funded through the Government’s Regional Infrastructure Fund (RIF), administered by Kānoa – the Regional Economic Development & Investment Unit. It also forms part of our 30‑Year Infrastructure Strategy (30YIS), which accelerates essential flood‑protection upgrades across the region.

The project includes removing the old structure and building new floodgates in the same location, starting with environmental controls, site setup, fencing, and public access changes. The upgraded structure will improve flood resilience, make maintenance safer for staff, and provide much better fish passage.

To keep the stopbank track open during construction, a temporary bridge will be installed over Courtenay Stream next to the work area.