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Wontons, Hemp and Wool

An innovative solution to flood remediation with community benefits.

The Scour Bays project exemplifies a transformative approach to flood resilience, integrating nature-based solutions into flood management strategies. By prioritising native plant use, the project not only enhances ecological diversity but also establishes a framework for sustainable river management practices that can be replicated across the region. As Environment Canterbury continues to innovate, the lessons learned from this initiative promise to reshape the landscape of flood recovery and ecological stewardship in South Canterbury.
 

Scour Bay on the Orari River
Scour Bay on the Ōrāri River in late 2022. Willow poles in foreground and anchored tree protection in front of the groyne structure towards the stopbank at the rear.
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Background

In 2020 and 2021, South Canterbury faced unprecedented flooding, with events like the May 2021 deluge hitting the region with rainfall levels akin to a once-in-200-year occurrence. The resulting devastation affected both public infrastructure and private properties, necessitating a robust response from the regional council Environment Canterbury (ECan). Traditionally, flood remediation relied heavily on engineered solutions such as gravel groynes and willow poles. However, the increasing call from the community and Rūnanga partners for greater biodiversity and reduced dependence on low-diversity willow stands prompted a critical reevaluation of these practices.
 

Opportunity for Innovation

With supplementary central government funding at hand, ECan seized the opportunity to innovate within its flood recovery program. The Scour Bays project emerged as a pivotal initiative aimed at transforming flood-damaged areas into multi-functional, biodiversity-rich flood resilience assets. The project focused on trialling native plant species as integral components of flood protection infrastructure, challenging the long-standing reliance on willow.
 

Sketch outlining proposed ‘Terrafelt Trench’ construction, overlaid on a scour bay on the North Branch of the Ashburton River.
Proposed Terrafelt Trench construction

Project Implementation

The Scour Bays project set out to establish native vegetation in recently eroded river gravels using novel planting techniques and geotextile materials. Key innovations included machine-assisted planting and hydrophilic, wool-based geotextiles, which addressed the stressful conditions of scour bays and embankments. This strategic approach aimed to accelerate the growth rates of native species, positioning them as viable alternatives to the rapid colonisation provided by willows.

Within the first year, the results were promising. Native plants thrived in harsh environments, exhibiting growth rates comparable to both willows and established natives in more favourable conditions. The findings underscored the potential for native vegetation to bolster flood protection and enhance local biodiversity.

 

Broader Impact and Benefits

The Scour Bays project is part of the larger Berm Transition project, which aims to reshape flood-impacted landscapes into resilient ecosystems. The initiative not only targets improved flood management but also seeks to:

  • Enhance indigenous biodiversity by nurturing a wide variety of native flora and fauna.
  • Promote Kaitīakitanga, aligning with the values of mana whenua partners and protecting mahinga kai.
  • Foster community engagement through local contracting, job creation, and improved recreational access to the rivers.

 

Challenges and Future Directions

Despite its successes, the project faced challenges, including the use of materials like Terrafelt, which is not fully biodegradable. In response, Environment Canterbury collaborated with Advance Landscape Systems to develop a new, fully biodegradable weed mat made from wool and hemp fibres. Trials are currently underway to evaluate this alternative on the Mason and Waiau Rivers, paving the way for future applications.

Protection comparison
Comparison of growth rates of phormium tenax / harakeke, also showing austraderia richardii / toe-toe and coprosma robusta / karamū) shown with (right) and without (left) Terrafelt at the same site. The plants were protected by the biodegradable NaturGuard supplied by Advance Landspace Systems.
 
Enter: Wonton Bag

In a further step towards eco-friendly solutions, Advance Landscape Systems partnered with Environment Canterbury and local councils to create the Wonton Bag, a biodegradable planting bag designed to replicate the benefits of Terrafelt. Utilising FuturFiber material in a blend of New Zealand wool and hemp, this innovative bag is fully biodegradable and produced in Canterbury. The name “Wonton Bag” was playfully coined by a council staff member who remarked on its resemblance to a wonton. Currently undergoing trials, the Wonton Bag promises to be an effective, environmentally friendly option for planting alongside riverbeds, reinforcing the commitment to ecological restoration in the region.
 
 
Wonton Bag Wonton Bag 1

FuturFiber™ Hemp Wonton Planting Bag - specially designed to establish native plants in areas where there is little or no planting media. They are made from 50% NZ grown Hemp fibres and 50% dag wool fibres and are completely biodegradable.
 
Find out more:
- View full report by Environment Canterbury here: Berm Transition Project: Scour Bay Regeneration, Native Plants as Flood Protection Assets
- Read other case studies here
- Discuss solutions for challenges facing your area with one of our consultants.