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Funded: $768,000 by MBIE (climate resilience) 
Total project cost: $1.2m
Project duration: 2 years
Jobs expected over project life: 14

This project will complete the final section of stopbank on the Piako Flood Protection Scheme to the agreed level of service design height.

Ngātea is reliant on flood protection infrastructure, originally built in the 1960s, for protection from both tidal surge and Piako River flooding. The population of Ngātea is increasing, reflecting its desirability as a rural location with ready access to local, regional and national parklands as well as the Firth of Thames.

The flood protection infrastructure, particularly earth stopbanks, may have limited opportunities to adapt to climatic changes. The current approach of increased stopbank height and mass may have limited viability on the Hauraki Plains due to the underlying strength of the marine mud on which they are built. In 2017, a top up to the stopbank adjacent to Ngātea caused cracking and slumping in three places.

This project includes a trial upgrade section on the stopbank to give greater understanding of the upper soil loading limit of the marine mud to establish the long-term viability of current stopbank design as flood protection infrastructure.  Alternative stopbank design approaches may need to be developed if the ability to increase stopbank height is proven limited.

Benefits:

  • Additional resilience for communities, including in food production and employment growth.
  • Protects State Highway 2 and 27, therefore more surety of travel between Auckland and Tauranga or the Coromandel Peninsula.
  • Advancing the understanding of failure modes associated with stopbanks founded on marine mud soils.
  • Creation of an underground drain to enable the room required to increase the height of the stopbank.

Key activities:

  • Trial upgrade completed: monitoring of the trial site showed we need to upgrade stopbanks more slowly and avoid the placement of large volumes of soil on the river side of the stopbank.
  • Haywards floodgate decommissioned.
  • Kaihere Road kerb and channel works completed.
  • Creation of ramps to improve rowing club’s access to the jetty complete.
  • Improvement works to three stopbank slumps adjacent River Road.
    Works beginning on the trial upgrade of a stopbank.
    A stopbank is really just a big pile of dirt.
    Trial upgrade completed, with the stopbank covered in hay for erosion protection while grass grows underneath.
    Sheetpiles in Ngātea Town support the stopbank and will be coated to extend their life.
    [1/4] Works beginning on the trial upgrade of a stopbank.

    Factsheets

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