Murihiku Slow the Flow

Taking a whole catchment approach to flood resilience

Murihiku Slow the Flow was a pilot programme jointly delivered by Te Ao Mārama Inc. and Environment Southland. Focused on the upper Mataura catchment, Murihiku Slow the Flow tested how a collaborative approach — bringing together technical, cultural and place-based knowledge — could be used to assess the potential for nature-based solutions to reduce flood risk and improve catchment-wide environmental wellbeing.

The urgency for this work increased after the February 2020 floods, which resulted in the evacuation of more than 4,500 people from communities within the Mataura catchment. The river’s degraded condition and over-allocated waters further highlighted the need for integrated, long-term approaches to flood risk reduction, ecosystem health and community resilience.

As climate change intensifies and increases the frequency of extreme weather, reducing the peak flow of the Mataura River remains crucial for downstream communities, such as Gore and Mataura.

Supported by funding from the Ministry for the Environment, Murihiku Slow the Flow was one of 21 regional pilot programmes that ran from mid-2023 to mid-2025, funded by Jobs for Nature – Mahi mō te Taiao. The programme produced a draft ‘blueprint’ for an integrated catchment approach to floodplain management in Murihiku Southland. The work has now been completed.

Toitū te marae o Tāne
Toitū te marae o Tangata
Toitū te Iwi
When the land and waters are strong, so are the people.

This guiding principle sat at the heart of Murihiku Slow the Flow — recognising that flood risk reduction, environmental health and community wellbeing are connected.

What are nature-based solutions?

Nature-based solutions are actions that protect, restore or manage ecosystems to tackle issues like flooding, while also improving biodiversity and people’s wellbeing. They work with natural processes, rather than against them, and can complement engineering solutions or 'hard' infrastructure.

In practice, that can include:

Detention/retention features (e.g. detainment bunds, ponds, swales) that temporarily hold water to lower flood peaks.
Wetland restoration/creation to soak up and slowly release rainfall.
Native vegetation and soil management to increase infiltration and reduce runoff.
Re-connecting rivers with their floodplains so water can spread safely in big events.

Put simply, nature-based solutions mimic natural water pathways to slow, store and filter water across the whole catchment, from the headwaters to the floodplain.

What the programme showed (in brief)

Working as a system: Nature-based solutions are most effective when implemented as a system-wide, integrated package that mimics natural water cycles — slowing, storing and filtering water from headwaters to floodplains, rather than relying on isolated fixes.
Potential impact of nature-based solutions: The magnitude of the potential reductions depends on the scale of deployment (coverage), location, design and sequencing. For example, floodplain reconnection without added roughness/vegetation can increase peak flows by allowing water to move more quickly across the floodplain.
Partnership is key: Collaboration between Environment Southland and Te Ao Marama Inc. brought cultural frameworks, place-based insight and priorities that shaped how potential nature-based solutions were assessed for the study area.
Value beyond flooding: Flood-mitigation benefits alone may not justify the combined investment in nature-based solutions alongside engineering solutions. However, broader environmental and cultural co-benefits (explored qualitatively via the rural More Than Water prototype) contribute additional value.
Tools for decision-making: Scenario modelling and the rural More Than Water Tool prototype helped visualise trade-offs when considered alongside local and cultural knowledge.

Want to learn more?

Get the key results and insights in one place: download the Murihiku Slow the Flow Insights Report. This report distils two years of collaborative work and recommendations for future flood risk reduction in Murihiku Southland.

Contact project lead Dr Ella Lawton - ella.lawton@es.govt.nz

Part of Murihiku Southland’s climate response

Murihiku Slow the Flow provides us with a tested process or 'blueprint' for evaluating, agreeing on and planning future upgrades to the flood infrastructure network to reduce flood risk, including how nature-based solutions can be considered alongside traditional infrastructure:

It complements other Environment Southland projects, including:

Detailed flood modelling to understand and plan for risk
Our Regional Climate Change Strategy for Murihiku Southland

Did the programme build anything?

It didn't involve constructing any new works. Instead, it developed and tested an assessment approach by combining existing information with site visits and hīkoi, knowledge sharing, modelling, and adapting decision-support tools, including the rural More than Water Tool.

How do nature-based solutions relate to the existing flood infrastructure network?

They complement the existing network. The modelling compared a nature-based solutions package against business-as-usual (which includes the existing flood banks). Nature-based solutions can work alongside traditional assets to help reduce flood effects.

What would success look like if options were progressed?

A balanced set of outcomes: reduced peak flows and risk to people and property, improved catchment health and progress against cultural and community indicators — measured over time.

What does this mean for landowners and communities now?

No immediate changes. Any near-term works will focus on maintaining and upgrading existing flood infrastructure to agreed levels of service. If new or expanded works are proposed, engagement will be proportionate to the scale and potential effects. Ngāi Tahu ki Murihiku (via Te Ao Mārama Inc.), councils, landowners, Waka Kotahi NZTA, KiwiRail and other stakeholders will be involved early to discuss options, understand potential impacts, and explore how works could be designed, consented and resourced before any decisions are made. Wider community engagement will also be part of this process, so communities understand proposals and can provide input where appropriate.

Do the scenarios explored through Murihiku Slow the Flow change insurance settings?

No. The process explored through Murihiku Slow the Flow has the potential to produce outputs that inform planning rather than determine insurance outcomes. Insurers consider many factors when setting premiums or deciding whether to offer cover. The programme has produced a 'blueprint' for incorporating nature-based solutions into future flood risk decision-making and planning. Over time, well-designed works, informed by this approach, can help maintain or improve insurability. Without progressing this kind of work, the risk of higher premiums, exclusions or loss of cover increases, shifting more cost and risk to households and councils.