Assessment of the Nukupure Park Foreshore Projects: Beach Nourishment, Dune Planting, and Toa. April 2019.

Assessment of the Nukupure Park Foreshore Projects: Beach Nourishment, Dune Planting, and Toa (April 2019).

Assessment of the Nukupure Park Foreshore Projects: Beach Nourishment, Dune Planting, and Toa. A Kirkwood, J Flanagan. 2019. [].
Prepared for Ngati Teaia, landowners of Nukupure Park by Andy Kirkwood and Justine Flanagan.
Contact: [firstName] @


In Feb 2019 public works were completed along the Nukupure Park shoreline in Muri, Rarotonga, Cook Islands. Beach Nourishment and Dune Planting by the Cook Islands government (through the Mei Te Vai Ke Te Vai Project), and community group Muri Environment Care were intended as a coastal protection measure in response to observed beach-loss.

  • Late Feb 2019 sediment was collected from the Vaiterenga stream delta (alongside The Pacific Resort) and placed on the upper beach / dune along Nukupure Park Beach. Sediment was retained with coconut matting (coir).
  • Early March over 80 community volunteers planted 3000 native plants along the dune.
  • Mar-Apr the Muri coastline experienced heavy rains and surface flooding.
  • Mid-April 2019 inland floodwaters destablised the park edge and eroded the back of the artificial dune area.

Project Status at April 2019

  • The dune has collapsed along the south-east edge of the park.
  • The coconut matting intended to retain nourishment has instead hardened the coastline and is accelerating sand-loss.
  • With the removal of shoreline armour and the collapse of the dune, the park(land) is now exposed to wave-action and is eroding.
  • The shallow-rooted toa/ironwood roots are inundated with salt-water at high-tide and are starting to die. Taller trees are approx. 20m high and subject to easterly winds gusting 45-50km. Uprooted trees will further erode the park.
  • Public safety is also a consideration as the recreational area is along a shoreline popular with tourists.

The report references recent and historical research into the Muri coastline and lagoon environment; and the Environmental Impact Assessment and funding applications for the projects. Site observations were carried out Feb―Apr 2019. An additional site visit documented erosion impacts after heavy rain/flooding Apr 17―18 (this flooding also closed the main road through Muri).

Cross-referencing the plants proposed for the dune area has led to research on the toa / ironwood trees (Casuarina equisetifolia L.). Toa have been planted along the park edge and are a common feature of the island’s coastline. They are planted with the intent of stablising the dune area and/or as a wind-break. However, as it grows, the tree flattens the slope (profile) of the beach and dune area. Toa results in beach-loss and accelerated coastal erosion.


Assessment of the Nukpure Park Foreshore Projects: Beach Nourishment, Dune Planting, and Toa

Classification/subjects: coastal protection, coastal erosion, Rarotonga, Cook Islands, South Pacific islands, climate change, flooding, toa, casuarina, ironwood, Nukupure Park, Muri lagoon, Muri Environment Care, Mei Te Vai Ki Te Vai, Te Mato Vai, beach restoration, beach nourishment, dune planting/vegetation, dune stabilisation.


Table of Contents


  • Erosion of the Nukupure Park Coastline
  • Muri Shoreline Projects
  • Project Assessment
  • Assessment Method
  • Site Observations Feb-Apr 2019
  • Next Steps


  • Plant Selection
  • Foreshore Protection
  • A Wrapped Dune
  • Fencing and Pedestrian Beach Access


  • Supporting Evidence


  • Project Status to April 2019
  • Predictions


  • Project Status to April 2019
  • Predictions


  • Toa: Quick Facts
  • Toa in the Cook Island
  • Dune Stabilisation
  • Toa and Coastal Erosion


  • Public Perception



  • Defining the Problem and Project Aims
  • Additional Research Required
  • Solutions to Seaweed Growth




List of Figures

  • Fig. 1 Erosion to Nukupure Park, c. 4 Jan 2019
  • Fig. 2 Nukupure Park Beach Nourishment Engineering Cross-section (modified)
  • Fig. 3 Nukupure Park Site Visit, 23 Feb 2019
  • Fig. 4 Beach Nourishment Construction, 23 Feb 2019
  • Fig. 5 Pedestrian Access, 27 Mar 2019
  • Fig. 6 Dune Fencing Methods, EIA / MEC
  • Fig. 7 Map Showing Muri Shoreline Characteristics
  • Fig. 8 Example Beach Profile from Nukupure Coastline: Rugby 2
  • Fig. 9 Completed Beach Nourishment and Planting, 12 Mar 2019
  • Fig. 10 Nukupure Park Beach Nourishment Engineering Cross-section (modified)
  • Fig. 11 Erosion Impacts
  • Fig. 12 Erosion Impacts, 27 Mar 2019
  • Fig. 13 Dune Planting Area, 12 Mar 2019
  • Fig. 14 Plantings, 12 Mar 2019
  • Fig. 15 Toa Branchlets, 27 Mar 20195
  • Fig. 16 Dune Erosion and Leaf Litter, 27 Mar 2019
  • Fig. 17 Toa along the Muri Shoreline, 23 Feb 2019
  • Fig. 18 Casuarina Intrusion, Bahamas (From Sealey, 2011)
  • Fig. 19 Aerial View of the Muri Shoreline 1991 / 2017 showing Nukupure Park
  • Fig. 20 Nukupure Beach c.1980 / 2018
  • Fig. 21 Erosion impacts: Centre-field, 19 Apr 2019
  • Fig. 22 Erosion impacts, 19 Apr 2019
  • Fig. 23 Pedestrian Accesses, 19 Apr 2019
  • Fig. 24 Erosion Impacts, Lagoon-side North-east Corner, 19 Apr 2019
  • Fig. 25 Erosion Impacts, North-east Corner, 19 Apr 2019
  • Fig. 26 Toa 19 Apr 2019
  • Fig. 27 Fishermen walking toward the reef over the Koromiri-sandbar at high-tide, 27 Apr 2019
  • Fig. 28 Vetiver Grass and Coconut Palms
  • Fig. 29 Shoreline Armour (Muri), 23 Feb 2019

References and Further Reading

Coastal Environment

  1. Contemporary Coastal Protection on Rarotonga Cook Islands. University of Canterbury, T Alan T Utanga, 1996.
  2. (PDF) Volcanic Geology of Rarotonga, Southern Pacific Ocean. New Zealand Journal of Geology and Geophysics, G. M. Thompson, J. Malpas & Ian E. M. Smith, 1998.
  3. (PDF) Cook Islands Priority Environmental Problems (PEC) Report: A Review and Assessment of the Priority Environmental Concerns. T Rongo, J Rongo, Island Friends, International Waters Pacific Technical Report no. 11, South Pacific Regional Environment Programme, 2004.
  4. Mitigating Shore Erosion Along Sheltered Coasts. (USA) National Academies Press, 2007.
  5. (PDF) Preliminary Field Observations of Muri Shoreline and Lagoon. E Beetham, T Turner, 2016.
  6. (PDF) Environmental Impact Assessment: Sediment Removal at the Vaiterenga Stream and Beach Nourishment at Nukupure Park. Mei Te Vai Ki Te Vai, Dr Murray Wallis, 2017.
  7. (PDF) Ministry of Marine Resources / AECOM Interdisciplinary Assessment of the Muri Lagoon: Final Report Consolidating the Sanitation Development Upgrade for the Cook Islands Government. Jonathan McCue et al, 2018.
  8. Nukupure Beach Coastal Protection: Application to Global Environment Fund, Small Grants Programme. Muri Environment Care, Mann Short, 2018.
  9. Nukupure Beach Coastal Protection: Presentation to Ngati Teaia by Muri Environment Care. Jamie Short, Feb 2019.


  1. Disappearing Beaches: Dune Stabilisation, []. Dr J Floor Anthoni, 2000.
  2. (PDF) The Cycle of Casuarina-induced Beach Erosion ― A Case Study from Andros, Bahamas. Neil Sealey, 2003.
  3. Cook Islands Bio-diversity Database. Gerald McCormack, Cook Islands Natural Heritage Trust, 2003―.
  4. (PDF) Casuarina-induced Beach Erosion Revisited 2011. Neil Sealey, 2011.
  5. (PDF) Australian Pine, Casuarina equisetifolia L. Management Plan for Florida Recommendations from the Australian Pine Task Force. April 2013.
  6. (PDF) Vetiver and Coastal Erosion: Case Study from Brazil. Veticon Consulting,, 2017.
  7. (PDF) Coastal Stabilisation Using Vetiver Grass. Vetiver Network International, 2017.
  8. Vetiver Network International [].

News Items


Updated: 21 May 2019.


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