Current river works
Here you can find information on our current river maintenance works we are undertaking across the region through targeted rates from river rating districts.
This includes operational tasks such as:
- weed control
- tree maintenance or removal
- infrastructure inspections.
Monthly river works plan: We also provide a monthly work plan that provides an overview of upcoming and current river works operations by area and river. Download the work plan—Kaikōura to Waitaki (PDF file, 3.5MB).
Annual work plans: Find out what flood protection and drainage scheme maintenance activities are planned in your rating district from July 2025 to June 2026. Download work plans: southern region (PDF file, 2.7MB), northern region (PDF file, 1.86MB), central region (PDF file, 3.7MB)
Need more information or help? Contact our customer advisory team via our online form or call 0800 324 636.
Note: Dates given are indicative, as weather may delay work completion.
Southern black-backed gull control
WHAT: Southern black-backed gull control
WHERE: Waimakariri River below the gorge and the lower Hakatere Ashburton River
WHEN: Starting Monday 10 November 2025 for a maximum of five days (works may be delayed to the following week pending river or weather conditions).
We are controlling Southern black-backed gull (SBBG) populations on the Lower Waimakariri River and the lower Hakatere Ashburton River using alpha-chloralose. Signs will be placed at public entrance points while this is carried out.
These rivers are ecologically important as nesting habitat for protected bird species (including black-fronted tern, black-billed gull, banded dotterel and wrybill) which rely on braided river systems for their nesting success and species survival. SBBG are not a protected species and are a known predator of the eggs and chicks of braided river bird species.
The aim of the control operation is to reduce populations of Southern black-backed gulls, as effectively and humanely as possible, without compromising the safety of non-target species or the general public. A bird survey will be completed prior to works starting, to ensure we avoid any non-target species.
Application of the toxin will occur on a maximum of two days, following three to five days of pre-feeding non-toxic bait, to condition the birds to eating the bait. All carcasses and unused bait will be removed as soon as the operation is complete.
4WDs and/or rafts will be used to access the island site. A helicopter will be used to assist with clean up and to scout the general area for carcasses, which will be disposed of by a certified waste disposal company.
Read more about why we carry out this important control work.
Poynters Nature Reserve yellow flag iris control
WHAT: Targeted control of yellow flag iris
WHERE: Poynters Nature Reserve, Kaiapoi
WHEN: 6-8 weeks from 1 November to 31 December 2025
We’re carrying out targeted control of yellow flag iris in the wetland at Poynters Nature Reserve from early November, with work expected to finish before the end of December.
Yellow flag iris is an unwanted organism under the Biosecurity Act, declared by the Ministry for Primary Industries (MPI) because of the serious threat it poses to native ecosystems and livestock. The plant can quickly spread through waterways, displacing native vegetation, altering river flow, and its leaves and rhizomes are toxic to stock.
Its rhizomes (underground stems) make it especially difficult to control, as even small fragments can be carried by water and grow into new plants. Control at this site will be undertaken carefully using a knapsack-applied herbicide, targeting only the affected areas. We will be operating under our Resource Consent CRC222040 and the EPA permission STRG-06-06-2022-014.
Signage will be in place at public access points within 100 metres of the treatment area before spraying begins and will remain for five days after work is completed.
Learn more about why and how we control weeds in Waitaha Canterbury.
The work will take place in the red area
Ōtukaikino weed control
WHAT: Weed control and native plant maintenance
WHERE: True right of Ōtukaikino Stream, directly downstream from the Clearwater Avenue bridge
WHEN: 1 November 2025
We’re removing regrowing willows, old man’s beard, and other exotic plants that threaten the health of recently planted natives. We’ll use a mix of methods including drill-and-fill on tree stumps, cut-and-paste on smaller plants and vines, and targeted spraying of some seedlings.
We'll place signage at the site entrance when work begins.
The work will take place in the red area
Tree removal – Ruataniwha/Cam River stopbank
WHAT: Tree removal
WHERE: True right of Ruataniwha/Cam River at Cox Road
WHEN: November to December 2025
We are removing topped willows along wide sections of the berm as part of the Ruataniwha/Cam River flood protection upgrade.
Trees will be removed using an excavator with a grapple saw, working from the top of the stopbank to reduce disruption. If access is limited, trees will be manually felled and winched to the excavator.
All material will be processed and stacked along the stopbank before being carted off site.
Felling signage and lookouts will be in place during works. Traffic management will be required for one day during the loading and carting phase.
The work will take place in the red area
Waitarakao/Washdyke/Seadown stopbank and drainage retreat project
WHAT: Tree removal at two locations in Washdyke, Timaru
WHERE: Timaru District Council land, about 150 metres south of Aorangi Road (site one) and between Hilton Haulage Ltd and Timaru District Council land (site two)
WHEN: Mid-November 2025 to 20 December 2025
The Waitarakao/Washdyke/Seadown drain and stopbank project helps prepare for climate change by moving the existing drain and coastal stopbank between Waitarakao Washdyke Lagoon and Beach Road in the Seadown drain scheme.
As part of the realignment work, we will be removing macrocarpa trees at two sites in Washdyke in the existing Seadown Drain Rating District.
The work involves cutting down the trees, mulching the material, and leaving stumps as close to ground level as possible. Mulch will be spread across the grass at each site, and the area will be tidied up when finished.
Signage will be installed around the area to inform the community of the work. The works are on land not generally accessed or used by the public.
Work will take place at two sites in Washdyke
Regional targeted weed control - aerial
WHAT: Weed control using helicopters for aerial weed spraying
WHEN: Mid-November to December 2025 for South Canterbury, early February to late March 2026 regionwide, as weather permits
WHERE: Canterbury Rivers: fairways, access tracks, stopbanks and around the rivers and drains listed below.
Southern rivers
Hook River aerial work
Otaio River aerial work
Upper Waitaki aerial work
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.
Why do we control weeds in the riverbed?
Healthy waterways are crucial 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, and we need to manage weeds for flood control and biodiversity protection. Left unchecked, invasive weeds are a significant flood risk, occupying the channel and forcing flood waters towards neighbouring communities and farmland. Weed growth can also contribute to the loss of aquatic habitats and nesting areas for native birds.
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.
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.
- Read EPA’s statement about glyphosate and information about how glyphosate is regulated in New Zealand
Regional targeted weed control - ground-based
WHAT: Ground-based weed control spraying across Canterbury
WHEN: September 2025 to March 2026
WHERE: Canterbury Rivers: fairways, access tracks, stopbanks and around the rivers and drains listed below.
Northern rivers
- Kaikōura Rivers (Kowhai, Lukes Creek, Middle Creek, Harnetts Creek, Floodgate Creek, Waimangarara, Lyell Creek)
- Kaikōura Drains
- Waiau Uwha River
- Chatterton/Rodgerson River
- Hurunui River
- Ashley river
Waimakariri-Eyre-Cust rivers
- Waimakariri River
- Eyre River
- Cust River
- Cam River
- Kaiapoi River
Central rivers
- Ashburton Hinds Drainage Scheme
- Halswell Drainage Scheme
- Ashburton River (including the main stem, North Branch, South Branch, Taylors Stream, Bowyers Stream, Pudding Hill Stream)
- Hinds River
- Halswell River
- Okana River
- Okuti River
- Opuahou Stream
- Hukahuka Turoa Stream
- Rakaia River
- Selwyn River
- Hororata River
- Hawkins River
- Waianiwaniwa River
Southern rivers
- Hook Drain
- Waihao River
- Waitaki River
- Upper Waitaki Rivers (Takapo, Pukaki, Ohau)
- Taumatakahu
- Te Aitarakih
- Seadown Drains
- Clandeboye Drains
- Rangitata River
- Orari River
- Waihī River
- Temuka River
- Ōpihi River
- Tengawai River
- Opuha rivers
- Pareora River
- Makikihi River
- Otaio River
Why do we control weeds in rivers
Our rivers are vulnerable to invasive weed infestations, and we need to manage harmful weeds for flood control and biodiversity protection. Left unchecked, invasive weeds contribute to significant flood risk by occupying the channel, which can obstruct natural water flow and redirect floodwaters onto riverbanks or stopbanks. This can cause erosion and put critical flood protection infrastructure at risk. Weed growth can also contribute to the loss of aquatic habitats, nesting areas for native birds and reduce native plant populations.
Our qualified staff and contractors carry out weed control measures in the open riverbeds within our drainage channels and on our berms and stopbanks, to help protect our communities from flooding and enhance biodiversity values.
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.
- Read EPA’s statement about glyphosate and information about how glyphosate is regulated in New Zealand
- Learn more about why and how we control weeds in rivers
Ashley Rakahuri karoro/southern black-backed gull control
WHAT: Karoro/southern black-backed gull control
WHERE: Ashley Rakahuri River
WHEN: September 2025 to February 2026
We are conducting a karoro/southern black-backed gull control operation from September 2025 until February 2026 – the nesting season for karoro – targeting eggs and nests at the Ashley River/Rakahuri.
Rakahuri is home to a number of rare, threatened bird species that nest on the riverbed, such as tarapirohe/black-fronted tern, tarāpuka/black-billed gull, ngutu pare/wrybill, and tūturiwhatu/banded dotterel.
The aim of the control operation is to displace the karoro population from the estuary as effectively and humanely as possible by removing eggs and nests, without compromising the safety of non-target species or the public.
This is to discourage karoro from using the site for future nests, thus assisting with the recovery of threatened braided river bird species. It is hoped the karoro will move further out of the hapua, making it more available for the rest of the estuary’s diverse bird population.
We are also working with Ngāi Tūāhuriri on egg removal for mahinga kai/mahika kai, which relates to the traditional value of food resources and their ecosystems, as well as the practices involved in producing, procuring, and protecting these resources.
The orange is the area where karoro nest
Rakitata/Rangitata River vegetation removal
WHAT: Rakitata/Rangitata River vegetation removal.
WHERE: Rakitata/Rangitata River, above the Arundel Bridge.
WHEN: October 2025 for a period of around one month.
We are mechanically removing vegetation from within the fairway of the Rangitata river. This is to increase flood capacity by widening the fairway through constricted areas, and to encourage braiding through the mobilisation of gravels. The vegetation that will be removed consists of pest species such as gorse, broom, wilding willows and pines.
Three discrete areas have been identified above the Arundel Bridge for targeted vegetation removal and ripping of gravels. The areas have been sprayed earlier this year as part of this project. The removed vegetation will be mulched offsite.
The work will occur in the areas marked red