Dredging at Vai Te Renga stream mouth / Muri Beach nourishment protection works / Mei Te Vai Ki Te Vai

Cook Island Erosion: Foreshore project not halting erosion

The Nukupure Park coastline is at risk of increased erosion. This was revealed in the April 2019 assessment report of the Nukupure Park foreshore projects of beach nourishment, dune planting and toa prepared by Andy Kirkwood and Justine Flanagan for Ngati Teaia; landowners of the area.

According to the report, the Mei Te Vai Ki Te Vai (MTVKTV) environmental impact assessment (EIA) proposes that shoreline retreat and narrowing of the beach may be due to historical sand mining in the area.

The erosion of Nukupure Park has two main dimensions such as erosion of the parkland and erosion of the beach, and the people hope to retain the park land and create conditions that result in a naturally sustained recreational beach.

At the same time the report shows that toa/ironwood trees are causing coastal erosion.

The likely impacts of the tree on Nukupure Park shows that toa are self seeding or planted and are maintained as a wind break for the recreational area. As they grow, the trees stabilises and flattens the dune area and in storm coastal conditions, waves erode the dune and eventually the park edge.

The report shows that in observing exposed roots the community armour the park edge and fill around the roots of the trees. The continued impact of the toa and lack of a dry beach prevents natural dune regeneration: in normal coastal conditions sand cannot be blown up off the beach to rebuild the dune, thus showing beach loss and coastal erosion.

Meanwhile, the report further states that unmanaged floodwater is affecting the land and between 2018 and 2019 the sand ramp area was washed out into the lagoon three times. In 2019 the north east end of the park suffered severe erosion along the park edge.

The report shows that between February and April this year alone, floodwaters have eroded the dune and sediment has been lost from above the dune bank and around the roots of the established trees along the edge of the park. The dune has been undermined and water courses have formed down the dune face.

It further shows that the coir matting has ripped and is losing plants, sand, and plastic pegs into the lagoon, a vertical slope (scarp) has formed at the base of the dune. The coir matting has hardened the coastline, accelerating beach loss according to the report.

The assessment report states that “it is likely that the beach nourishment and planting project plan will not prevent erosion of the coastline” nor enable natural beach regeneration. Failure of the dune will result in further loss of the park and beach. There will also be impacts on the lagoon and nearby coastal properties.

A site visit by the researcher late last month showed that the extreme weather conditions on April 18-19 resulted in flooding and road closure in Muri and erosion along the shorelines increased.

Overall the report stated that the beach nourishment and planting projects required further research into the causes of erosion and re-scoping to enable beach regeneration at Nukupure Park.

See Cook Islands News article . . .