Ōreti floodplain project

The Ōreti floodplain project is focused on the lower Ōreti catchment. It supports communities, including Winton and Dipton West, by strengthening the flood infrastructure network so it performs as intended during high flows. Winton is a key service town on State Highway 6, providing healthcare, education and emergency services to the broader rural community.

By 2040–2050, the Ōreti catchment is expected to experience around 10 percent more rainfall and a 13 percent increase in river flows. Without ongoing investment, this places sustained pressure on flood banks and channels and can lower service levels over time.

The first construction season focused on priority works for Dipton West — restoring sections of the flood bank to their design standard, addressing deferred maintenance, and improving channel performance to sustain agreed service levels. New co-funding, announced in October 2025, extends the Ōreti floodplain project. Further stages are being scoped and sequenced as design, modelling and engagement progress, so works can be targeted where they provide the greatest reduction in flood effects and continued benefits for the wider catchment.

This programme is co-funded with central government through Kānoa under the Resilient River Communities initiative and supported by the Regional Infrastructure Fund (RIF).

Read more about flood risk for Winton and the flood scheme’s level of protection here.

Tree removal - Dipton West

From mid-March 2026, Environment Southland has been removing invasive willow trees from approximately 15 hectares along the Ōreti River and Dipton West area.

This work forms part of the Ōreti Floodplain Project, which aims to strengthen the flood infrastructure network so it performs as intended during high river flows.

Our contractors may need access to land with staff, vehicles, and machinery to:

Remove selected willow trees and vegetation affecting flood bank stability
Reinstate access ramps and tracks
Manage vegetation and green waste responsibly.

David Milligan Park – temporary access closure

Access to David Milligan Park is temporarily closed while tree removal works are underway along the Ōreti flood bank near Dipton West.

Trees are being removed where they are growing into the flood bank or within the floodway, as they can weaken the bank or trap debris during floods. This work allows the flood bank to be properly reinstated so the flood scheme continues to function as intended.

The flood bank helps manage high river flows and reduce the damaging impacts of flooding on the Dipton West community, nearby properties and critical regional infrastructure. It also reduces the risk of disruption to key roading connections, including the Ōreti River bridge at Dipton, supports emergency access and reduces the need for reactive repairs after flood events.

The park will reopen once this work is completed.

Why are the trees being removed?

The trees in this area are growing both into the flood bank and within the floodway, and they affect the flood system in different ways.

Trees growing on flood banks can weaken the bank structure over time. Large roots can create pathways for water through the bank, and if trees fall or are blown over they can pull out large root balls, leaving holes that can become failure points during floods.

Trees growing in the floodway can also affect how water moves through the river during high flows. When trees or branches break off during floods, the wood can move downstream and become trapped against bridges, culverts or other structures, which can partially block flows or cause damage.

Removing trees in these locations allows the flood bank to be reinstated properly so the flood scheme can continue to function as intended.

What is happening with the wood from the trees?

The trees from David Milligan Park are being felled and the stumps removed where they have grown into the flood bank so the bank can be reinstated.

The wood is being removed off site. Trucks bringing in new topsoil to reinstate the flood bank are backloading the felled timber, so material can be removed efficiently.

For the wider project, a waste minimisation approach will be used:

Usable logs and timber will be retained for landowner use where practicable
Smaller material will be chipped and removed off site.
Only residual, non reusable material will be disposed of by controlled burning.

Controlled burning is a permitted activity under the Regional Air Plan. Burns will take place in designated gravel pits, under suitable weather conditions, with active supervision and on site fire suppression. Work will stop if smoke or nuisance effects extend beyond the site. Neighbouring landowners and emergency services will be notified in advance.

Why are the stumps being removed?

Where trees have grown into the flood bank, the stumps and roots need to be removed so the bank can be properly rebuilt.

The flood bank is then reinstated with suitable material and topsoil so grass cover can be re-established. Grass cover helps protect the bank from erosion during high flows.

Will this affect local traffic?

The flood bank works themselves are not affecting local traffic movements.

Dipton Castlerock Road is currently closed as part of a separate Southland District Council project to replace the Dipton bridge. That closure runs from 19 January to 30 April 2026. Residents can still access properties up to the bridge closure. For updates on that project, residents can contact Southland District Council on 0800 732 732.

Who is funding this work?

This work is being delivered by Environment Southland with support from central government through Kānoa – the Regional Economic Development & Investment Unit.

It forms part of a wider programme of flood infrastructure maintenance and upgrades across Murihiku Southland under the Resilient River Communities initiative.

Project overview

The Ōreti floodplain project delivers targeted upgrades to priority parts of the Ōreti flood infrastructure network to improve performance during major floods and prepare for projected increases in river flows.

Strengthen priority flood bank sections to reduce erosion, improve river stability, and increase channel capacity during high flows.
Remove pest trees (including crack willow) to reduce erosion and congestion—particularly near critical infrastructure such as the Winton and Centre Bush bridges.

Further stages will be added and sequenced as monitoring and modelling are updated.

Why this work matters

These works sustain agreed service levels for flood banks and channels in high-risk sections, reduce erosion risk and improve conveyance during high flows. Together, they reduce the direct impacts of flooding on people, property, productive land and critical services, and help shorten disruption after events.

Benefits

Risk reduction: improved flood bank performance and channel capacity during major flows.
Asset stewardship: addressing deferred maintenance now lowers future repair needs and costs.
Co-benefits: stabilised margins and reduced sediment help the river system function more effectively.
Local delivery: delivered by experienced Southland contractors, supporting local employment and efficient on-the-ground delivery.

Recently completed flood bank works near Dipton. Vegetation has been cleared from the flood bank, fencing has been relocated to improve grazing management, and the bank has been mown to promote healthy grass cover and support ongoing maintenance.

Funding and collaboration

This work is delivered by Environment Southland with experienced local contractors and partners. It forms part of the Resilient River Communities initiative and Environment Southland’s Before the Deluge 2.0 programme, co-funded with central government through Kānoa – Regional Economic Development & Investment Unit.

Looking ahead

Environment Southland is undertaking flood modelling across the region, prioritising areas with the highest flood risk, including the upper Ōreti catchment. This model will enable us to assess current flood protection levels, identify risks of flood bank breaches, evaluate potential infrastructure improvements, and explore nature-based solutions and land-use changes to reduce flood impacts.

See how local contractors contribute to on-the-ground flood infrastructure works across Murihiku Southland in this recent Envirosouth feature:
Holding the Line – Envirosouth, Spring 2025