Waiau River flood damage remediation

Environment Southland has undertaken flood damage remediation work in the lower-to-mid reaches of the Waiau River. This project was on farmland and provides river edge protection to the Waiau above Te Waewae (Waiau) Lagoon.

Te Waewae (Waiau) lagoon is culturally important to Ngāi Tahu ki Murihiku. It is ecologically significant and widely used by the community. The lagoon is particularly susceptible to various impacts, including effects from fine-sediment input, partly because the lagoon is long and narrow, and the outflow into Te Waewae Bay is narrow.

Flooding in Southland in October 2019 eroded large areas of riverbank throughout the lower Waiau River. With no flood protection in place, productive farmland was at risk of further erosion, with the likelihood of sediment washing down into the lagoon causing environmental damage.

In early 2020 remedial work was carried out under urgency on three properties. However, the February 2020 flood event halted progress. Funding received via the Kānoa - Regional Economic Development & Investment Unit within the Ministry for Business Innovation and Employment has enabled further work to be carried out at seven sites across four properties.

The project was completed in January 2022, with the river edge protection in place and the sites re-grassed and re-fenced.

The work

Rock was transported from quarries and other sites throughout Western Southland to the erosion sites on the Waiau River and placed along eroding banks. Two local firms undertook the work: Drainage & Excavation Services Ltd, Winton, and Nightcaps Contracting Ltd.

Benefits

• Protection for productive farmland and peace of mind for landowners
• Reduce sedimentation washing into Te Waewae (Waiau) lagoon
• Re-grassing and re-fencing funded through the project undertaken by local contractors