Whangamatā dune restoration / construction

Name of case study

Whangamatā dune restoration / construction

Location

Whangamatā, Bay of Plenty, New Zealand

Location

2023

Scale

Urban/Landscape scale

Area / size

700m length of cost

NbS employed

Artificial sand dunes; Dune preservation

Type of NbS

Ecosystem restoration; Ecosystem protection; Hybrid living/engineered interventions

Initiator

Coastcare Waikato, a partnership between local communities, iwi, district councils and Waikato Regional Council

Funder

Thames-Coromandel District Council and Waikato Regional Council, and directly affected landowners

Budget

Not available

Design group

Not available

Climate change benefits
  • Coastal erosion / wave attenuation
  • Coastal inundation 
  • Sea level rise
Societal / socio-cultural benefits
  • Climate change adaptation
  • Disaster risk reduction
Ecological benefits
  • Disturbance prevention (erosion, storm damage, flooding etc.)
  • Habitat provision

Summary of case study

Following the Cyclone Gabrielle in February 2023, which saw up to 20 meters of coastal erosion in some areas of Aotearoa New Zealand (Green, 2024), Whangamatā beach suffered destruction of much of the dunes at the Southern End (Ocean and Community Dynamics at Play in Dune Restoration, 2023). Coastcare Waikato, a community collaboration between iwi (tribes), local government, and local communities employed a soft engineering “whole of dune approach”, involving removing exotic planting from any remaining dunes, and then burying this, followed by reshaping of the new dune face using earth working equipment. Planting native dune species allows natural dune-building processes to resume trapping sand and building up of the sand dunes as a protective buffer to future coastal erosion (Makowski et al., 2013).

In Whangamatā, Coastcare Waikato reshaped and replanted newly constructed dune faces along 750m of coastline, protecting the housing directly landward of the beach. Sand was harvested from the mid beach and reshaped on the dunes at the land edge (Ocean and Community Dynamics at Play in Dune Restoration, 2023). This was the preferred option over hard engineered solutions like seawalls which can exacerbate coastal erosion by deflecting wave energy. The benefit of using a soft engineered dune, is that there is no material (fencing or engineered structures) to be exposed in the future, and the shifting beach landscape can continue through naturally fluctuating erosion and deposition processes (Magliocca et al., 2011).

Planting of locally appropriate native ōwhangatara/spinifex and pīngao dune grasses was carried out by community members including local land owners and schools (Ocean and Community Dynamics at Play in Dune Restoration, 2023). These species accrete sand to continue building dunes seaward, naturally increasing the dune buffer zone over time. Coastcare Waikato has used similar methods to rebuild dunes in multiple other locations in the region, at Kūaotunu, Tairua, Greys Beach and Cooks Beach (Caring for Our Coast, 2024).

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References
  • Caring for our coast. (2024). Thames Coromandel District Council. https://www.tcdc.govt.nz/Our-Community/Council-Projects/Current-Projects/Caring-for-our-Coast
  • Green, K. (2024, February 7). Cyclone Gabrielle: Parts of East Coast lost 10 metres of shoreline, research shows. RNZ. https://www.rnz.co.nz/news/national/508569/cyclone-gabrielle-parts-of-east-coast-lost-10-metres-of-shoreline-research-shows
  • Magliocca, N. R., McNamara, D. E., & Murray, A. B. (2011). Long-term, large-scale morphodynamic effects of artificial dune construction along a barrier island coastline. Journal of Coastal Research, 276, 918–930. https://doi.org/10.2112/JCOASTRES-D-10-00088.1
  • Makowski, C., Finkl, C. W., & Rusenko, K. (2013). Suitability of recycled glass cullet as artificial dune fill along coastal environments. Journal of Coastal Research, 289, 772–782. https://doi.org/10.2112/12A-00012.1Ocean and community dynamics at play in dune restoration. (2023). Waikato Regional Council. https://www.waikatoregion.govt.nz/story-hub/ocean-and-community-dynamics-at-play-in-dune-restoration/

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