Wyndham flood protection upgrade
Environment Southland is upgrading existing stop banks in Wyndham township (population 550 +). The aim in the near term is to provide a more robust and continuous flood defence scheme by focusing on areas that present the most risk to the community in the event of flooding in the short term. Once completed, the re-grassed stop banks will appear similar to the existing structures.
Wyndham flood protection upgrade is a Resilient River Communities project. Resilient River Communities is a joint initiative between Kānoa - the Regional Economic Development & Investment Unit, regional councils, and local authorities focused on developing and upgrading vital river management and flood protection schemes in Aotearoa New Zealand.
By having resilient river communities, we hope to minimise environmental, economic, and social damage caused by flooding – making New Zealand safer for everyone.
Extensive flooding in Murihiku Southland in February 2020 saw stop banks in Wyndham tested by floodwaters to near capacity. Emergency management and council staff, alongside Southland emergency services, evacuated 4500+ people throughout the Mataura catchment, including residents in Wyndham.
The Wyndham stop banks were built in the early 1970s following widespread flooding in 1968. They were raised again after severe flooding hit the region again in 1978. The stop banks guard the town against the Mataura River to the north, west and south and its tributary, the Mimihau Stream, to the north.
The work
- Widening the stop bank east of Wyndham Road and extending it 100 m to the east. This section of stop bank has low points, ponding, and areas of stock plugging.
- East of Wyndham Racecourse, three sections of stop bank are being widened, with buttresses constructed at the riverward toe. The work will address seepage at a section of stop bank east of the racecourse and an area with potential stability issues close to Mimihau Stream.
- North and west of Wyndham Racecourse the stop bank has low points, cattle pugging and instability. Several stands of trees have grown close to the base of the stop bank, some of which have been felled. The stumps and roots have the potential to affect stability and increase seepage. Works involve removing trees, tree stumps and roots close to the stop bank and reconstructing the stop bank throughout this entire section.
- At Ferry Street, a new approx. 200 m section of stop bank is being constructed to fill the gap. There is an existing drain running to the west of the new section of stop bank, which can remain in place. However, some of the recently planted vegetation near the new stop bank is being uplifted and replanted.
Inspection, repair and extension of the existing culverts, headwalls and flat gates and associated flood protection infrastructure is being undertaken along with the remedial works.
Benefits
- ‘Future proofed’ design so the height of the upgraded stop banks could be more easily raised in the future
- Provide flood protection where there is none by filling in gaps in the existing network
- Provide greater protection for homes and businesses in Wyndham
- Central government funding has enabled this work to be bought forward in the long term plan and at a much lower cost to the community
Project status (14 March 2023)
- Preliminary tree work completed
- Survey, geotechnical and engineering design work completed
- Engagement with landowners ongoing
- Community engagement underway
- Stockpiling of additional stop bank materials for 2022-23 construction season
- Consents and approvals finalised
- Construction contract awarded to Linton Contracting Ltd. December 2022
- Contractors on site from 16 January 2023
- Majority of tree work completed
- Culvert replacements underway
- Construction underway east of Wyndham Racecourse to widen and strengthen the Mimihau stop bank
Next steps
- Commence work on stop banks adjacent to Wyndham Racecourse and Ferry Street
- Expected completion of Wyndham Flood Protection Upgrade by late May 2023
