Vetiver in Rarotonga, Cook Islands: Researching alternative solutions to waste water management, erosion control, and slope retaining

Vetiver in the Cook Islands: Researching Alternative Solutions to Waste Water Management, Erosion Control, and Slope Retaining for Rarotonga.
A Kirkwood, J Flanagan, 2019.
[www.islandbooth.com/comm/vetiver-rarotonga-cook-islands.html].
Compiled by Andy Kirkwood and Justine Flanagan.

Contact: [firstName] @ islandbooth.com.

 

This page is a working draft: updated 23 May 2019. It provides background information and links to research about vetiver grass and the Vetiver System.

 

From 2017— Rarotonga, Cook Islands is the site of a number of large-scale transformative infrastructure projects, including water supply and disinfection, roading, drainage, waste-water management and treatment. How we approach these projects will have a long-term impact on the health of our community — and the health of our island.

Vetiver Grass

Vetiver grass (Chrysopogon zizanioides L.) is a fast-growing, deep-rooted plant that has been used internationally as a low-cost, environmentally-friendly alternative to traditional ‘hard’ engineering solutions. The grass is the foundation of the Vetiver System (VS), researched methods to address a wide-range of agricultural, infrastructure, and environmental management challenges.

Vetiver in the Cook Islands

Vetiver was introduced to the Cook Islands to the island of Atiu as a source of perfume for massage oil [1], then propogated in response to siltification of the central fresh water source. [citation needed]. It has also been used as erosion control in the makatea (fosilised coral) islands of Mangaia, Atiu, Mauke and Mitiaro [2].

In the capital island of Rarotonga:

  • The grass was promoted to the public as part of the Lagoon Day community-led environmental-awareness initiative (2008-2015).
  • Agriculture have planted-out areas of unsealed road as erosion control.
  • A residential property in Muri has been planted in the grass demonstrating its use to retain cut-slopes.
  • The grass has also been used along the wetland/stream areas of the Muri coastline to protect residential and tourism properties.

Considering Vetiver Solutions for Rarotonga

The way that vetiver grows make it suitable for a range of uses.

  • Surface erosion protection. Dense leaves slow waterflow (this reduces rutting). The leaves trap and hold sediment and organic matter; preventing it from entering waterways.
  • Drainage. The deep-penetrating root system (with growth of 2m+ in the first year), enables infiltration. Surface water meeting the base of the leaves is directed into the ground down the root path. The root system is also highly absorbent; in ideal conditions 1kg of dry shoot biomass (foliage/leaves) will use 6.8L/day [3].
  • Protection of upstream water sources for drinking water supply — prevents sediment and animal waste from entering waterways.
  • Filtering and biological treatment of waste water (septic/effluent). Rapid growth absorbs large volumes of fluid and nutrients. Beneficial bacteria and microbes process/remove harmful chemicals.
  • Coastal erosion protection: vetiver is salt-tolerant and can survive regular exposure to sea-water. Roots stabilise erosion-prone areas such as sand banks/dunes and the foreshore.

A Third World Solution to First World Problems

Barriers to the uptake of the Vetiver System may be its origin, and how information about the plant has been disseminated.

Vetiver grass is native to India. From the mid-1980s the World Bank encouraged research into uses of plant; to enable tropical and semi-tropical developing nations to address agriculture and infrastructure challenges.

Research and implementation of the Vetiver System was furthered by non-government organisation The Vetiver Network (now The Vetiver Network International). Vetiver Network publications such as Vetiver Grass – A Hedge Against Erosion (PDF) are practical guides written for fieldworkers and farmers [4].

Although the plant and its application has been extensively researched, it is often lesser-known by civil engineers from temperate, First World countries.

At the same time, urbanisation and changes in government policy can result in a loss of community-knowledge. In Fiji, vetiver-hedges were introduced in 1956 to retain soil and as moisture control [5]. In the 70s and 80s the Fiji government priority shifted from land conservation and the use of vetiver; to farming of sloping land for export. Local knowledge and use of vetiver declined.

Climate change impacts due to shifting sea-levels and changing weather patterns — along with the scale of such impacts — now make necessary investigation of low-cost sustainable biological solutions such as the Vetiver System.

Classification/subjects: vetiver grass, Chrysopogon zizanioides, coastal protection, coastal erosion, Rarotonga, Cook Islands, South Pacific islands, climate change, flooding, Mei Te Vai Ki Te Vai, waste water treatment, effluent, septic systems.

 

References and Further Reading

References

Cook ISlands Government / Infrastructure Project Management Units

Infrastructure Cook Islands has formed separate teams to manage large-scale infrastructure projects.

Septic Treatment using Vetiver Grass

Erosion Control using Vetiver Grass

Slope Retaining using Vetiver Grass

[coming soon]

Technical Specification for Vetiver Grass

Vetiver plant biology, application and planting methods.

 

Updated: 23 May 2019.

 
 

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